Summary of Significant Accounting Policies (Policies)	12 Months Ended
Dec. 31, 2025
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the United States Securities & Exchange Commission (“SEC”). Any reference in these notes to applicable guidance is meant to refer to U.S. GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) promulgated by the Financial Accounting Standards Board (“FASB”).
Principles of Consolidation and Redeemable Noncontrolling Interest	Principles of Consolidation and Redeemable Noncontrolling Interest The accompanying consolidated financial statements include the accounts of AT Umbrella LLC and its 100% wholly owned subsidiaries. AT Umbrella LLC is a Variable Interest Entity (“VIE”), as defined in ASC Topic 810 (“ASC 810”), Consolidation. ASC 810 requires the consolidation of VIEs in which the entity is defined as the primary beneficiary of the VIE. To be a primary beneficiary, an entity must have the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance, among other factors. The Company has assessed its variable interests in this entity and determined that the Company is the primary beneficiary of AT Umbrella LLC and its subsidiaries. In completing the assessment, the Company identified the activities that it considers most significant to the economic performance of this entity and determined that the Company has the power to direct those activities. As a result, AT Umbrella LLC and its subsidiaries’ financial position and results of operations are consolidated in the Company’s balance sheet and statement of operations. All significant intercompany balances and transactions have been eliminated in consolidation. The assets and liabilities of AT Umbrella LLC represent substantially all of the consolidated assets and liabilities of Andersen Group, Inc. Andersen Group, Inc., has not had any material operations on a standalone basis since its inception, and all of the operations of the Company are carried out by AT Umbrella LLC and its subsidiaries. A redeemable noncontrolling interest in a consolidated subsidiary represents the portion of the equity (net assets) in a subsidiary not attributable, directly or indirectly, to the Company. Redeemable noncontrolling interest is classified as temporary equity because the Class X Umbrella Units contained certain redemption features that were not solely within the control of the Company. The presentation of net income is modified to present earnings and other comprehensive income attributed to controlling and redeemable noncontrolling interests. The redeemable noncontrolling interest on the consolidated statement of operations represents the portion of earnings or loss attributable to the economic interest in AT Umbrella LLC held by Aggregator. See Note 12 for further information on the redeemable noncontrolling interest and the related accounting policies. The Company does not have any controlling interest in, and is not the primary beneficiary of, any other member firm of Andersen Global. Accordingly, these entities are considered related parties solely as a result of the memberships in the Swiss verein discussed above. These member firm entities are not consolidated in the Company’s financial statements.
Variable Interest Entity	One of the non-U.S. Andersen Global member firms is a VIE. The Company has assessed its variable interests in this entity and determined that the Company is not the primary beneficiary. In completing the assessment, the Company identified activities it considers most significant to the economic performance of this entity and determined that the Company does not have the power to direct those activities. As a result, that entity’s financial position and results of operations are not consolidated in the Company’s balance sheet and statement of operations. The Company's carrying value and exposure to loss is comprised of loans to the VIE included in loans and notes receivable from affiliates, net of allowance for credit losses and amounts due from the VIE included in prepaid expenses and other current assets.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. These estimates include but are not limited to the assessment of the recoverability of goodwill and intangible assets, valuation and expected lives of tangible and intangible assets, allowance for credit losses, certain accrued liabilities, and valuation allowance on deferred tax assets. Due to the inherent uncertainty in making those assumptions, actual results could differ from those estimates.
Segment Information	Segment Information ASC Topic 280, Segment Reporting establishes standards for reporting information about operating segments. Operating segments are defined as components of an enterprise where discrete financial information is available and evaluated regularly by the Chief Operating Decision Maker (“CODM”), in deciding how to allocate resources and in assessing performance. The Company’s CODM is the Chief Executive Officer (“CEO”). The Company operates in one segment based upon the financial information used by its CODM in evaluating the financial performance of its business and allocating resources. The single segment represents the Company’s core business of providing tax, valuation, financial advisory and related consulting services to its clients. See Note 19 for further information on the Company’s reporting segment.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash equivalents include demand deposits, money market funds, and highly liquid debt securities with maturities when acquired of three months or less. As of December 31, 2025 and 2024, the Company maintained cash balances in interest-bearing and non-interest-bearing cash deposit accounts. As of December 31, 2025 and 2024, the Company had substantially all of its cash deposited at one large financial institution, with balances that are in excess of federally insured levels. The Company regularly monitors the financial stability of its financial institutions and believes that it is not exposed to any significant credit risk in cash and cash equivalents. Interest and other income for the years ended December 31, 2025, 2024 and 2023 includes interest earned by the Company on its short-term cash equivalent investments and interest-bearing bank deposits of $3.4 million, $2.9 million and $1.5 million, respectively.
Accounts Receivable and Allowance for Credit Losses	Accounts Receivable and Allowance for Credit Losses The Company’s accounts receivable are recorded at amounts billed to clients and are presented on the consolidated balance sheet net of an allowance for credit losses. The Company’s unbilled services are services performed, but not yet billed to clients and are presented as a component of accounts receivable on the consolidated balance sheet at net realizable value and net of an allowance for credit losses. The Company estimates its allowance for credit losses based on historical experience, the age of the receivable balances, and current and future economic conditions, among other factors that may affect the Company’s ability to collect from clients.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that may be subject to concentration of credit risk consist primarily of cash and cash equivalents and accounts receivable. The Company places its cash and cash equivalents with highly-rated financial institutions. The Company has not experienced any losses on its deposits of cash and cash equivalents. The Company’s client base consists of a broad range of individuals and businesses in a variety of industries primarily located throughout the United States. No single client accounted for more than 10% of revenue or accounts receivable for the years ended December 31, 2025, 2024 and 2023. The Company believes that the geographic and industry diversity of its client base throughout the United States minimizes the risk of incurring material losses due to concentrations of credit risk.
Fair Value Measurement	Fair Value Measurement Fair value accounting is applied for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements on a recurring basis, at least annually. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Assets and liabilities recorded at fair value in the consolidated financial statements are categorized based upon the level of judgment associated with the inputs used to measure their fair value. Hierarchical levels, which are directly related to the amount of subjectivity, associated with the inputs to the valuation of these assets or liabilities, are as follows: Level 1: Observable inputs, such as quoted prices in active markets for identical assets and liabilities. Level 2: Inputs other than the quoted prices in active markets that are observable either directly or indirectly. Level 3: Unobservable inputs, in which there is little or no market data which require the Company to develop its own assumptions. Observable inputs are based on market data obtained from independent sources. Unobservable inputs reflect the Company’s assessment of the assumptions market participants would use to value certain financial instruments. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. The categorization of financial instruments within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The carrying amounts of certain financial instruments, including cash held at financial institutions, accounts receivable and accounts payable approximate fair value due to their short-term maturities. See Note 5 for more information on the fair value of financial assets and liabilities.
Property and Equipment	Leasehold improvements and office equipment acquired under finance leases are amortized over the lesser of the term of the related lease or the estimated useful lives of the assets. Expenditures for replacements and betterments are capitalized and expenditures relating to maintenance and repairs are charged to expense as incurred.
Leases	Leases The Company determines if an arrangement is or contains a lease at inception by assessing whether the arrangement contains an identified asset and whether it has the right to control the use of the identified asset over the term of the arrangement. Right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Lease liabilities are recognized at the lease commencement date based on the present value of future lease payments over the lease term. To determine the present value of lease payments, the Company uses the implicit interest rate, if it is readily determinable or estimable. To the extent that the Company is unable to utilize an interest rate implicit in the lease, the collateralized incremental borrowing rate is used based on the information available at the lease commencement date, in determining the present value of lease payments. ROU assets are based on the measurement of the lease liability and include any lease payments made prior to or on lease commencement and initial direct costs incurred and exclude lease incentives, as applicable. The Company has elected not to separate lease and non-lease components for any leases within its existing classes of assets, therefore the Company accounts for lease and non-lease components as a single lease component. Payments under the Company’s lease arrangements are primarily fixed; however, certain lease arrangements contain variable payments, which are expensed as incurred and not included in the measurement of the ROU assets and lease liabilities. These amounts include payments for common-area maintenance, real estate taxes, and utilities which are based on usage or performance. Lease terms may include options to extend or terminate the lease when it is reasonably certain the Company will exercise any such options. The Company has made the policy election to exempt leases with an original term of less than 12 months, including any renewal or extension options that are reasonably certain to be exercised and that do not include a purchase option whose exercise is reasonably certain, for all classes of underlying assets to which the right of use relates. Operating leases are included in operating right-of-use assets, operating lease liability, current and operating lease liability, noncurrent line items in the Company’s consolidated balance sheets. The Company recognizes lease expense for its operating leases on a straight-line basis over the term of the lease. Finance leases are included in property and equipment, net, other current liabilities, and other liabilities in the Company’s consolidated balance sheets.
Capitalized Internal Use Software	Capitalized Internal Use Software The Company incurs development costs related to its internal use software. The Company capitalizes these software development costs incurred during the application development stage, including activities such as designing, coding, testing, and implementing software to create functional and deployable solutions. Costs related to preliminary project activities and post implementation activities are expensed as incurred. Once the project is substantially complete and ready for its intended use, these costs are amortized on a straight-line basis over the estimated useful life of the software, generally three years. Costs capitalized as internal-use software development costs include eligible salaries and compensation-related costs of employees and costs incurred in developing new features and enhancements when the costs will result in additional functionality. Capitalized internal use software is classified as intangible assets, net on the consolidated balance sheets.
Implementation Costs for Cloud Computing Arrangements	Implementation Costs for Cloud Computing Arrangements The Company incurs costs to implement cloud computing arrangements that are service contracts including eligible salaries and compensation-related costs of employees and third-party consulting fees. The Company capitalizes costs incurred during the application development stage of a project. These costs are amortized on a straight-line basis over the term of the hosting service contracts, including renewal periods that are reasonably certain to be exercised. These costs are recognized as a component of sales, general and administrative expenses on the consolidated statement of operations. Capitalized implementation costs primarily relate to the implementation of the Company's ERP system, which was launched in 2021. As of December 31, 2025, the Company continues to progress with additional functionality and integrations. These capitalized costs are included as a component of prepaid expenses and other current assets on the Company's consolidated balance sheets. As of December 31, 2025 and 2024, capitalized implementation costs for cloud computing arrangements totaled $0.5 million and $1.2 million, respectively, net of accumulated amortization. During the years ended December 31, 2025, 2024 and 2023, the Company recognized amortization of capitalized implementation costs of $2.1 million, $0.9 million and $0.9 million, respectively.
Intangible Assets	Intangible Assets Intangible assets resulting from the acquisition of entities are accounted for using the acquisition method based on management’s estimate of the fair value of assets received. Intangible assets are finite lived and mainly consist of client relationships, intellectual property, trademarks and tradenames. These intangible assets are amortized on a straight-line basis over their estimated useful lives. Client relationships and other intangible assets are amortized over a five-year period. Trade name and intellectual property assets are amortized over a three- and five-year period, respectively.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets, including property and equipment, right-of-use assets, and intangible assets, are tested for recoverability whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. The carrying amount of a long-lived asset is not recoverable if it exceeds the sum of the undiscounted future cash flows expected to result from the use and eventual disposition of the asset. The amount of impairment loss, if any, is measured as the difference between the carrying value of the asset and its estimated fair value. The Company estimates fair value based on the best information available, making necessary estimates, judgments, and projections. For purposes of these tests, long-lived assets must be grouped with other assets and liabilities at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities. The Company determined that there were no indicators that warranted a quantitative impairment analysis and therefore there were no impairment losses for the years ended December 31, 2025, 2024 and 2023.
Investments in Held-to-Maturity Debt Securities	Investments in Held-to-Maturity Debt Securities The Company maintains a portfolio of investments in U.S. Treasury securities at one large financial institution with maturities at the time of purchase of greater than 90 days up to two years. As the Company has the intent and ability to hold these securities to maturity, they are carried at amortized cost. Interest income and the amortization of discounts and premiums are recorded in interest income on the consolidated statements of operations. Interest income for the years ended December 31, 2025, 2024 and 2023 includes interest earned by the Company from held-to-maturity debt securities of $0.7 million, $1.5 million and $0.9 million, respectively. As of December 31, 2025 and 2024, the Company has not recognized an allowance for expected credit losses related to held-to-maturity securities as the holdings are all U.S. Treasury securities. The United States has a consistent high credit rating by rating agencies, a long history with no credit losses, is a sovereign entity that can print its own currency and has its currency routinely held by central banks as a reserve currency, and the market rate for U.S. Treasury securities is widely recognized as a risk-free rate. The Company has also not identified any unrealized losses for these investments attributable to credit factors. The Company does not intend to sell the investments before maturity, and it is not more likely than not that it will be required to sell the investments before recovery of its amortized cost basis.
Goodwill	Goodwill Goodwill reflects the excess of the consideration transferred, including the fair value of any contingent consideration, over the assigned fair values of the identifiable net assets acquired in a business combination. Goodwill is not amortized and is tested for impairment at least on an annual basis on October 1 or more frequently if facts or circumstances indicate that goodwill might be impaired. Goodwill is assessed for impairment using a qualitative or quantitative approach. Where the Company uses the qualitative assessment, first the Company determines if, based on qualitative factors, it is more likely than not that an impairment exists. Factors considered include historical financial performance, macroeconomic and industry conditions, and the legal and regulatory environment. If the qualitative assessment indicates that it is more likely than not that an impairment exists, then a quantitative assessment is performed. The quantitative assessment requires an analysis of several estimates including future cash flows or income consistent with management’s strategic business plans, annual sales growth rates and the selection of assumptions underlying a discount rate based on market data available at the time to determine fair value of the Company or reporting unit. If the fair value is less than the carrying amount an impairment charge for the difference is recorded. The Company concluded that based on the qualitative approach, there was no goodwill impairment during the years ended December 31, 2025, 2024 and 2023. There is no accumulated impairment as of December 31, 2025 and 2024.
Compensation Arrangements	Compensation Arrangements Deferred Compensation The Company established a loyalty retention program effective January 1, 2020, under which employees accrue loyalty bonuses based on their roles and qualifying service years. The Company accounts for this program in accordance with ASC 710, Compensation, and accrues for the bonus payments on a straight-line basis over the service period, and has made an accounting policy election to account for forfeitures as they occur. In 2025, the Company discontinued the program and made the final payment in August 2025. Effective January 1, 2023, the Company implemented a deferred compensation plan for non-partner employees holding the title of Director. The plan provides annual awards, the value of which is determined at the discretion of the Board of Directors. Payments are contingent upon the continued employment of participants during the five-year payment period. The Company accounts for this plan in accordance with ASC 710, whereby it accrues deferred compensation liabilities over the payment period. Liabilities are accrued using on a straight-line basis over the service period and are adjusted for changes, such as participant terminations. Cash payments are recorded annually as a reduction of the liability. Liabilities for these programs are recorded in current and non-current liabilities, depending on the anticipated timing of payment. Incentive Compensation Certain client-serving individuals are eligible for variable incentive compensation arrangements. These generally represent a fixed bonus percentage based upon revenue collected. In some cases, these individuals are subject to minimum guaranteed payments. The Company accrues for such arrangements on a monthly basis as amounts are earned. These costs are recorded as cost of services in the consolidated statements of operations. Equity-Based Compensation Equity-based compensation is accounted for as an expense in accordance with ASC Topic 718, Stock Compensation, which requires compensation cost for the grant-date fair value of equity-based awards to be recognized over the requisite service period. The Company uses the straight-line method to amortize all stock awards granted over the requisite service period of the award. The Company accounts for forfeitures when they occur, and any compensation expense previously recognized on unvested equity-based awards is reversed when forfeited. The fair value of restricted stock units and restricted Class X Aggregator Units is based on the fair value of the Class A common stock at the time of grant. The fair value of LTIP Units is estimated using a Monte Carlo simulation approach. These require management to make assumptions on the grant date, including the expected term of the award, the expected volatility of the Company’s Class A common stock calculated based on a period of time generally commensurate with the expected term of the award, risk-free interest rates, expected dividend yields of the Company’s Class A common stock, and the probability of achieving the hurdle amount. See Note 14 for a discussion of the Company’s equity-based compensation plans and awards. Profits Interest Prior to the IPO, the board of directors of Andersen Tax Holdings LLC was authorized to grant awards that qualify as profits interests for U.S. federal income tax purposes in accordance with the Company’s governing documents. Certain entities were awarded profits interests in the Company on behalf of certain executives and advisers and are considered related parties. These interests grant the recipients the right to certain cash distributions, based upon a percentage of license fees collected from certain trademarks of the Company. A profits interest award is accounted for based on its substance. A profits interest award that is in substance a profit-sharing arrangement or performance bonus would generally not be within the scope of the stock-based compensation guidance under ASC 718, and would be accounted for under the guidance for deferred compensation plans under ASC 710 similar to a cash bonus. However, if the arrangement has characteristics more akin to the risks and rewards of equity ownership, the arrangement would be accounted for under stock-based compensation guidance. The Company analyzes awards granted to recipients at the time they are granted or modified. The Company accounts for profits interest awards under ASC 710 as a cash bonus plan with performance conditions. The Company accrues compensation expense when it determines payment is probable and estimable, which is when the license fees are collected. The Company records the corresponding profits interest liability within other current liabilities or other liabilities on the consolidated balance sheets based on the estimated distribution date.
Revenue Recognition	Revenue Recognition Revenue primarily consists of professional service fees derived from tax, valuation, financial advisory and related consulting services. The Company recognizes revenue as the promised services are provided, in an amount that reflects the consideration which the Company expects to receive in exchange for those services. The Company recognizes revenue following a five-step model: (i) identify contract(s) with a client; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenues when (or as) the Company satisfies the performance obligation(s). For each performance obligation identified, the Company determines at contract inception whether it satisfies the performance obligation over time or satisfies the performance obligation at a point in time. If the Company does not satisfy a performance obligation over time, the performance obligation is satisfied at a point in time. In most of the Company’s client arrangements, the period between client payment and transfer of control of the service is expected to be one year or less. Therefore, the Company has elected the practical expedient to not adjust the amount of consideration for the effects of a significant financing component. Clients are generally billed for services using an hourly rate. Certain customers may receive discounts and price concessions, which are accounted for as variable consideration in determining the transaction price. The Company records revenue over time as services are performed and time and materials are charged to specific client codes. Contractual billings represent amounts that correspond directly with the value provided to the client (e.g., the number of hours worked at contractually agreed-upon rates), and revenue is recognized as amounts become billable in accordance with contractual terms. Certain of these contracts are contingent upon achieving contractual targets to collect the fee. Due to the uncertainty of the outcome and the probability that a change in estimate would result in a significant reversal of revenue, the Company has applied a constraint on recording contingent revenue. Revenue is recognized when the constraint has been lifted, which is the date when the contractual target has been achieved, or cash has been collected. Reimbursable expenses that are billed to clients, primarily relating to travel and out-of-pocket expenses incurred in connection with client engagements, are included in revenue, and an equivalent amount of reimbursable expenses is included in costs of services in the period in which the expense is incurred. The timing of billings and cash collections may result in unbilled services, accounts receivable and deferred revenue on the consolidated balance sheet. Amounts are billed either at periodic intervals (e.g., monthly or quarterly) or upon the achievement of contractual milestones. Payments received in advance of the client receiving a benefit is a contract liability and is presented as deferred revenue in the consolidated balance sheet. Deferred revenue that is expected to be recognized as revenue within one year is recorded as the current portion of deferred revenue and the remaining portion is recorded as non-current deferred revenue. The Company does not have non-current deferred revenue at December 31, 2025 and 2024. Other contract balances consist of accounts receivable (including both billed and unbilled services), net of allowance for credit losses.
Operating Expenses	Operating Expenses Cost of Services Cost of services primarily consist of direct expenses related to the production of deliverables under client assignments. This includes personnel costs for revenue-generating personnel, such as wages, benefits, equity-based compensation, incentive compensation, and sub-consultant costs, software costs, and an allocation of non-personnel costs such as occupancy costs. Sales, General and Administrative Sales, general and administrative expenses primarily consist of personnel costs such as wages, benefits, equity-based compensation, and incentive compensation related to support and administrative functions, and non-personnel costs such as professional fees, business development, occupancy, advertising, recruiting, and training costs. Advertising costs were immaterial during the years ended December 31, 2025, 2024 and 2023. Depreciation and Amortization Depreciation and amortization expenses primarily consist of depreciation and amortization of the Company’s property and equipment, capitalized software, and acquired intangible assets.
Income Taxes	Income Taxes Andersen Group Inc. is taxed as a C corporation and is subject to U.S. federal, state and local income taxes on its share of allocable partnership income. Andersen Group Inc.’s sole material asset is its ownership in AT Umbrella LLC, which is a limited liability company that is taxed as a partnership for U.S. federal and certain state and local income tax purposes. AT Umbrella LLC’s allocable share of taxable income and related tax credits, if any, are passed through to its members, including Andersen Group Inc., and are included in the members’ tax returns. In any period in which Andersen Group Inc. acquires additional units of AT Umbrella LLC by means of an exchange transaction, Andersen Group Inc. records the related income tax effects as an adjustment to equity. The Company accounts for income taxes in accordance with the asset and liability approach for financial accounting and reporting, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, the Company determines deferred tax assets and liabilities on the basis of the differences between the financial statement and tax bases of assets and liabilities by using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company recognizes deferred tax assets to the extent that the Company believes that these assets are more likely than not to be realized. In making such a determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If the Company determines that it would be able to realize deferred taxes in the future in excess of their net recorded amount, the Company would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions in accordance with ASC 740, Accounting for Income Taxes on the basis of a two-step process in which (1) the Company determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, the Company recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits as a component of income tax expense in the consolidated statements of operations. The Company’s policy for global intangible low taxed income (“GILTI”) is to treat as a period cost when incurred.
Amounts Payable to Related Parties Pursuant to Tax Receivable Agreement	Amounts Payable to Related Parties Pursuant to Tax Receivable Agreement In connection with the IPO and Reorganization Transactions, the Company entered into the TRA with certain pre-IPO owners that provides for the payment to certain holders of Class X Umbrella Units who are or may become parties to the TRA from time to time 85% of the amount of cash savings, if any, in U.S. federal, state and local income tax or franchise tax that the Company realizes or is deemed to realize (determined by using assumptions regarding combined state and local income tax rates) as a result of (i) any increase in tax basis in the assets of AT Umbrella LLC and its flow-through subsidiaries resulting from purchases of Class X Umbrella Units from such Class X Umbrella Unit holders with the proceeds of this offering or resulting from exchanges of Class X Umbrella Units for at Andersen Group Inc.’s election, shares of Class A common stock or cash in the future; and (ii) certain other tax benefits related to entering into the TRA, including tax benefits attributable to payments that are made under the TRA. The TRA will make certain simplifying assumptions regarding the determination of the cash savings that are realized or are deemed to realize from the covered tax attributes, which may result in payments pursuant to the TRA in excess of those that would result if such assumptions were not made. No party to the TRA will reimburse the Company for any payments previously made if such basis increases or other benefits are subsequently disallowed, except that excess payments made to the TRA parties will be netted against future payments that would otherwise be made under the TRA, if any, after determination of such excess. The Company accounts for amounts payable under the TRA in accordance with ASC Topic 450, Contingencies. As such, subsequent changes in the fair value of the TRA liability between reporting periods are recognized in the consolidated statement of operations. The Company has not yet incurred a liability in connection with the TRA.
Loss per Share	Loss per Share Basic loss per share is calculated by dividing the net loss by the weighted-average number of shares of the Company’s Class A common stock outstanding for the period, without consideration for potential dilutive shares of common stock. Shares of Class B common stock and RSUs are not entitled to receive any distributions or dividends and are therefore excluded from this presentation since they are not participating securities. The Company calculates diluted loss per share using the treasury stock method for RSUs and the if-converted method for redeemable Class X Umbrella Units and LTIP Units. For the period following the IPO and Reorganization Transactions through December 31, 2025, 98,294,464 Class X Umbrella Units were considered dilutive and have been included in the calculation of diluted net loss per share. The Company did not include earnings per unit for the pre-IPO period as part of its financial statements. All earnings prior to December 18, 2025, the completion date of the IPO, were entirely allocable to the redeemable noncontrolling interest and, as a result, earnings per share information is not applicable for reporting periods prior to this date. Consequently, only earnings per share for net loss for periods including and subsequent to December 18, 2025 are presented.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements Changes to U.S. GAAP are established by the FASB in the form of Accounting Standards Updates ("ASUs") to the FASB Accounting Standards Codification. ASUs issued which are not specifically listed below were assessed and have already been adopted in a prior period or determined to be either not applicable or are not expected to have a material impact on the Company’s consolidated financial statements and related disclosures. Recent Accounting Pronouncements Not Yet Adopted In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures (“ASU 2023-09”), which requires disclosure of disaggregated income taxes paid, prescribes standard categories for the components of the effective tax rate reconciliation, and modifies other income tax-related disclosures. Early adoption is permitted. Upon adoption, the guidance may be applied prospectively or retrospectively. For public business entities, the amendments are effective for fiscal years beginning after December 15, 2024. For entities other than public business entities, the amendments are effective for annual periods beginning after December 15, 2025. As an emerging growth company, the Company has elected the extended transition period for complying with new or revised accounting standards and this ASU has not yet been adopted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures. In November 2024, the FASB issued ASU 2024-03, Income Statement (Topic 220): Reporting Comprehensive Income - Expense Disaggregation Disclosures, Disaggregation of Income Statement Expenses ("ASU 2024-03"), which requires public business entities to disclose, in interim and annual reporting periods, additional information about certain expenses in the consolidated financial statements. The amendments in this ASU will be effective for annual periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Early adoption is permitted and is effective on either a prospective basis or retrospective basis. The Company is currently evaluating the potential impact that the adoption of this standard will have on its consolidated financial statements. In May 2025, the FASB issued ASU No. 2025-03, Business Combinations (Topic 805) and Consolidation (Topic 810): Determining the Accounting Acquirer in the Acquisition of a Variable Interest Entity (“VIE”), which provides clarifying guidance on determining the accounting acquirer in certain transactions involving VIEs. The update aims to improve consistency and comparability in financial reporting. The guidance will be effective for all entities for annual periods beginning after December 15, 2026, including interim periods within those annual periods. Early adoption is permitted. Upon adoption, the guidance will be applied prospectively. The Company is currently evaluating the potential impact that the adoption of this standard will have on its consolidated financial statements. In July 2025, the FASB issued ASU No. 2025-05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets, which added a practical expedient that assumes that current conditions as of the balance sheet date do not change for the remaining life of the asset when estimating expected credit losses for current accounts receivable and current contract assets. The guidance is effective for all entities for annual periods beginning after December 15, 2025. The Company plans to adopt this ASU on the effective date and does not expect it to have a material impact on its consolidated financial statements. In September 2025, the FASB issued ASU No. 2025-06, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Targeted Improvements in Accounting for Internal-Use Software, which replaced the “project stage” model with a principles-based framework for cost recognition and capitalization of internal-use software. The update requires companies to capitalize internal-use software costs when management authorizes and commits funding for the software project and when it is probable the project will be completed and the software will be used to perform the function intended. The guidance will be effective for all entities for annual periods beginning after December 15, 2027, including interim periods within those annual periods. Early adoption is permitted. Upon adoption, the guidance may be applied prospectively or retrospectively. The Company is currently evaluating the potential impact that the adoption of this standard will have on its consolidated financial statements. In September 2025, the FASB issued ASU No. 2025-07, Derivatives and Hedging (Topic 815) and Revenue from Contracts with Customers (Topic 606): Derivatives Scope Refinements and Scope Clarification for Share-Based Noncash Consideration From a Customer in a Revenue Contract. ASU 2025-07 introduces guidance for applying derivative accounting to contracts that include features tied to the operations or activities of one of the parties to the contract. It also aims to reduce diversity in how share-based payments are accounted for in revenue contracts. ASU 2025-07 will be effective for the annual periods beginning after December 15, 2026 with early adoption permitted. The Company is currently evaluating the potential impact that the adoption of this standard will have on its consolidated financial statements. In December 2025, the FASB issued ASU 2025-11, Interim Reporting (Topic 270) Narrow- Scope Improvements. The amendments in this ASU do not change the fundamental nature of interim reporting or expand or reduce current interim disclosure. The amendments in this ASU clarify the guidance in ASC Topic 270 by providing a comprehensive list of required interim disclosures and codifying a disclosure principle that requires the Company to disclose events and changes that occur after the end of the most recent annual reporting period that have a material impact on its consolidated financial statements. The amendments in this ASU are effective for interim periods within annual reporting periods beginning after December 15, 2027. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements. In December 2025, the FASB issued ASU 2025-12, Codification Improvements (Topic 815). The amendments in this ASU update the FASB Accounting Standards Codification for a broad range of Topics arising from technical corrections, unintended application of the Codification, clarifications, and other minor improvements. The amendments in this ASU are effective for all entities for annual periods beginning after December 15, 2026, and interim periods within those annual periods. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2025

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the United States Securities & Exchange Commission (“SEC”). Any reference in these notes to applicable guidance is meant to refer to U.S. GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) promulgated by the Financial Accounting Standards Board (“FASB”).

Principles of Consolidation and Redeemable Noncontrolling Interest

The accompanying consolidated financial statements include the accounts of AT Umbrella LLC and its 100% wholly owned subsidiaries. AT Umbrella LLC is a Variable Interest Entity (“VIE”), as defined in ASC Topic 810 (“ASC 810”), Consolidation. ASC 810 requires the consolidation of VIEs in which the entity is defined as the primary beneficiary of the VIE. To be a primary beneficiary, an entity must have the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance, among other factors. The Company has assessed its variable interests in this entity and determined that the Company is the primary beneficiary of AT Umbrella LLC and its subsidiaries. In completing the assessment, the Company identified the activities that it considers most significant to the economic performance of this entity and determined that the Company has the power to direct those activities. As a result, AT Umbrella LLC and its subsidiaries’ financial position and results of operations are consolidated in the Company’s balance sheet and statement of operations.

All significant intercompany balances and transactions have been eliminated in consolidation. The assets and liabilities of AT Umbrella LLC represent substantially all of the consolidated assets and liabilities of Andersen Group, Inc. Andersen Group, Inc., has not had any material operations on a standalone basis since its inception, and all of the operations of the Company are carried out by AT Umbrella LLC and its subsidiaries.

A redeemable noncontrolling interest in a consolidated subsidiary represents the portion of the equity (net assets) in a subsidiary not attributable, directly or indirectly, to the Company. Redeemable noncontrolling interest is classified as temporary equity because the Class X Umbrella Units contained certain redemption features that were not solely within the control of the Company. The presentation of net income is modified to present earnings and other comprehensive income attributed to controlling and redeemable noncontrolling interests.

The redeemable noncontrolling interest on the consolidated statement of operations represents the portion of earnings or loss attributable to the economic interest in AT Umbrella LLC held by Aggregator. See Note 12 for further information on the redeemable noncontrolling interest and the related accounting policies.

The Company does not have any controlling interest in, and is not the primary beneficiary of, any other member firm of Andersen Global. Accordingly, these entities are considered related parties solely as a result of the memberships in the Swiss verein discussed above. These member firm entities are not consolidated in the Company’s financial statements.

Variable Interest Entity

One of the non-U.S. Andersen Global member firms is a VIE. The Company has assessed its variable interests in this entity and determined that the Company is not the primary beneficiary. In completing the assessment, the Company identified activities it considers most significant to the economic performance of this entity and determined that the Company does not have the power to direct those activities. As a result, that entity’s financial position and results of operations are not consolidated in the Company’s balance sheet and statement of operations. The Company's carrying value and exposure to loss is comprised of loans to the VIE included in loans and notes receivable from affiliates, net of allowance for credit losses and amounts due from the VIE included in prepaid expenses and other current assets.

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. These estimates include but are not limited to the assessment of the recoverability of goodwill and intangible assets, valuation and expected lives of tangible and intangible assets, allowance for credit losses, certain accrued liabilities, and valuation allowance on deferred tax assets. Due to the inherent uncertainty in making those assumptions, actual results could differ from those estimates.

Segment Information

ASC Topic 280, Segment Reporting establishes standards for reporting information about operating segments. Operating segments are defined as components of an enterprise where discrete financial information is available and evaluated regularly by the Chief Operating Decision Maker (“CODM”), in deciding how to allocate resources and in assessing performance. The Company’s CODM is the Chief Executive Officer (“CEO”). The Company operates in one segment based upon the financial information used by its CODM in evaluating the financial performance of its business and allocating resources. The single segment represents the Company’s core business of providing tax, valuation, financial advisory and related consulting services to its clients. See Note 19 for further information on the Company’s reporting segment.

Cash and Cash Equivalents

Cash equivalents include demand deposits, money market funds, and highly liquid debt securities with maturities when acquired of three months or less. As of December 31, 2025 and 2024, the Company maintained cash balances in interest-bearing and non-interest-bearing cash deposit accounts.

As of December 31, 2025 and 2024, the Company had substantially all of its cash deposited at one large financial institution, with balances that are in excess of federally insured levels. The Company regularly monitors the financial stability of its financial institutions and believes that it is not exposed to any significant credit risk in cash and cash equivalents.

Interest and other income for the years ended December 31, 2025, 2024 and 2023 includes interest earned by the Company on its short-term cash equivalent investments and interest-bearing bank deposits of $3.4 million, $2.9 million and $1.5 million, respectively.

Accounts Receivable and Allowance for Credit Losses

The Company’s accounts receivable are recorded at amounts billed to clients and are presented on the consolidated balance sheet net of an allowance for credit losses. The Company’s unbilled services are services performed, but not yet billed to clients and are presented as a component of accounts receivable on the consolidated balance sheet at net realizable value and net of an allowance for credit losses. The Company estimates its allowance for credit losses based on historical

experience, the age of the receivable balances, and current and future economic conditions, among other factors that may affect the Company’s ability to collect from clients.

Concentration of Credit Risk

Financial instruments that may be subject to concentration of credit risk consist primarily of cash and cash equivalents and accounts receivable. The Company places its cash and cash equivalents with highly-rated financial institutions. The Company has not experienced any losses on its deposits of cash and cash equivalents.

The Company’s client base consists of a broad range of individuals and businesses in a variety of industries primarily located throughout the United States. No single client accounted for more than 10% of revenue or accounts receivable for the years ended December 31, 2025, 2024 and 2023. The Company believes that the geographic and industry diversity of its client base throughout the United States minimizes the risk of incurring material losses due to concentrations of credit risk.

Fair Value Measurement

Fair value accounting is applied for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements on a recurring basis, at least annually. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.

Assets and liabilities recorded at fair value in the consolidated financial statements are categorized based upon the level of judgment associated with the inputs used to measure their fair value. Hierarchical levels, which are directly related to the amount of subjectivity, associated with the inputs to the valuation of these assets or liabilities, are as follows:

Level 1: Observable inputs, such as quoted prices in active markets for identical assets and liabilities.

Level 2: Inputs other than the quoted prices in active markets that are observable either directly or indirectly.

Level 3: Unobservable inputs, in which there is little or no market data which require the Company to develop its own assumptions.

Observable inputs are based on market data obtained from independent sources. Unobservable inputs reflect the Company’s assessment of the assumptions market participants would use to value certain financial instruments. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. The categorization of financial instruments within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.

The carrying amounts of certain financial instruments, including cash held at financial institutions, accounts receivable and accounts payable approximate fair value due to their short-term maturities. See Note 5 for more information on the fair value of financial assets and liabilities.

Property and Equipment

Leasehold improvements and office equipment acquired under finance leases are amortized over the lesser of the term of the related lease or the estimated useful lives of the assets. Expenditures for replacements and betterments are capitalized and expenditures relating to maintenance and repairs are charged to expense as incurred.

Leases

The Company determines if an arrangement is or contains a lease at inception by assessing whether the arrangement contains an identified asset and whether it has the right to control the use of the identified asset over the term of the arrangement. Right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Lease liabilities are recognized at the lease commencement date based on the present value of future lease payments over the lease term. To determine the present value of lease payments, the Company uses the implicit interest rate, if it is readily determinable or estimable. To the extent that the Company is unable to utilize an interest rate implicit in the lease, the collateralized incremental borrowing rate is used based on the information available at the lease commencement date, in determining the present value of lease payments. ROU assets are based on the measurement of the lease liability and include any lease payments made prior to or on lease commencement and initial direct costs incurred and exclude lease incentives, as applicable.

The Company has elected not to separate lease and non-lease components for any leases within its existing classes of assets, therefore the Company accounts for lease and non-lease components as a single lease component. Payments under the Company’s lease arrangements are primarily fixed; however, certain lease arrangements contain variable payments, which are expensed as incurred and not included in the measurement of the ROU assets and lease liabilities. These amounts include payments for common-area maintenance, real estate taxes, and utilities which are based on usage or performance. Lease terms may include options to extend or terminate the lease when it is reasonably certain the Company will exercise any such options. The Company has made the policy election to exempt leases with an original term of less than 12 months, including any renewal or extension options that are reasonably certain to be exercised and that do not include a purchase option whose exercise is reasonably certain, for all classes of underlying assets to which the right of use relates.

Operating leases are included in operating right-of-use assets, operating lease liability, current and operating lease liability, noncurrent line items in the Company’s consolidated balance sheets. The Company recognizes lease expense for its operating leases on a straight-line basis over the term of the lease. Finance leases are included in property and equipment, net, other current liabilities, and other liabilities in the Company’s consolidated balance sheets.

Capitalized Internal Use Software

The Company incurs development costs related to its internal use software. The Company capitalizes these software development costs incurred during the application development stage, including activities such as designing, coding, testing, and implementing software to create functional and deployable solutions. Costs related to preliminary project activities and post implementation activities are expensed as incurred. Once the project is substantially complete and ready for its intended use, these costs are amortized on a straight-line basis over the estimated useful life of the software, generally three years. Costs capitalized as internal-use software development costs include eligible salaries and compensation-related costs of employees and costs incurred in developing new features and enhancements when the costs will result in additional functionality. Capitalized internal use software is classified as intangible assets, net on the consolidated balance sheets.

Implementation Costs for Cloud Computing Arrangements

The Company incurs costs to implement cloud computing arrangements that are service contracts including eligible salaries and compensation-related costs of employees and third-party consulting fees. The Company capitalizes costs incurred during the application development stage of a project. These costs are amortized on a straight-line basis over the term of the hosting service contracts, including renewal periods that are reasonably certain to be exercised. These costs are recognized as a component of sales, general and administrative expenses on the consolidated statement of operations. Capitalized implementation costs primarily relate to the implementation of the Company's ERP system, which was launched in 2021. As of December 31, 2025, the Company continues to progress with additional functionality and integrations. These capitalized costs are included as a component of prepaid expenses and other current assets on the Company's consolidated balance sheets.

As of December 31, 2025 and 2024, capitalized implementation costs for cloud computing arrangements totaled $0.5 million and $1.2 million, respectively, net of accumulated amortization. During the years ended December 31, 2025, 2024

and 2023, the Company recognized amortization of capitalized implementation costs of $2.1 million, $0.9 million and $0.9 million, respectively.

Intangible Assets

Intangible assets resulting from the acquisition of entities are accounted for using the acquisition method based on management’s estimate of the fair value of assets received. Intangible assets are finite lived and mainly consist of client relationships, intellectual property, trademarks and tradenames. These intangible assets are amortized on a straight-line basis over their estimated useful lives. Client relationships and other intangible assets are amortized over a five-year period. Trade name and intellectual property assets are amortized over a three- and five-year period, respectively.

Impairment of Long-Lived Assets

Long-lived assets, including property and equipment, right-of-use assets, and intangible assets, are tested for recoverability whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. The carrying amount of a long-lived asset is not recoverable if it exceeds the sum of the undiscounted future cash flows expected to result from the use and eventual disposition of the asset. The amount of impairment loss, if any, is measured as the difference between the carrying value of the asset and its estimated fair value. The Company estimates fair value based on the best information available, making necessary estimates, judgments, and projections. For purposes of these tests, long-lived assets must be grouped with other assets and liabilities at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities. The Company determined that there were no indicators that warranted a quantitative impairment analysis and therefore there were no impairment losses for the years ended December 31, 2025, 2024 and 2023.

Investments in Held-to-Maturity Debt Securities

The Company maintains a portfolio of investments in U.S. Treasury securities at one large financial institution with maturities at the time of purchase of greater than 90 days up to two years. As the Company has the intent and ability to hold these securities to maturity, they are carried at amortized cost. Interest income and the amortization of discounts and premiums are recorded in interest income on the consolidated statements of operations.

Interest income for the years ended December 31, 2025, 2024 and 2023 includes interest earned by the Company from held-to-maturity debt securities of $0.7 million, $1.5 million and $0.9 million, respectively. As of December 31, 2025 and 2024, the Company has not recognized an allowance for expected credit losses related to held-to-maturity securities as the holdings are all U.S. Treasury securities. The United States has a consistent high credit rating by rating agencies, a long history with no credit losses, is a sovereign entity that can print its own currency and has its currency routinely held by central banks as a reserve currency, and the market rate for U.S. Treasury securities is widely recognized as a risk-free rate. The Company has also not identified any unrealized losses for these investments attributable to credit factors. The Company does not intend to sell the investments before maturity, and it is not more likely than not that it will be required to sell the investments before recovery of its amortized cost basis.

Goodwill

Goodwill reflects the excess of the consideration transferred, including the fair value of any contingent consideration, over the assigned fair values of the identifiable net assets acquired in a business combination.

Goodwill is not amortized and is tested for impairment at least on an annual basis on October 1 or more frequently if facts or circumstances indicate that goodwill might be impaired. Goodwill is assessed for impairment using a qualitative or quantitative approach. Where the Company uses the qualitative assessment, first the Company determines if, based on qualitative factors, it is more likely than not that an impairment exists. Factors considered include historical financial performance, macroeconomic and industry conditions, and the legal and regulatory environment. If the qualitative assessment indicates that it is more likely than not that an impairment exists, then a quantitative assessment is performed. The quantitative assessment requires an analysis of several estimates including future cash flows or income consistent with management’s strategic business plans, annual sales growth rates and the selection of assumptions underlying a discount rate based on market data available at the time to determine fair value of the Company or reporting unit. If the fair value is less than the carrying amount an impairment charge for the difference is recorded. The

Company concluded that based on the qualitative approach, there was no goodwill impairment during the years ended December 31, 2025, 2024 and 2023. There is no accumulated impairment as of December 31, 2025 and 2024.

Compensation Arrangements

Deferred Compensation

The Company established a loyalty retention program effective January 1, 2020, under which employees accrue loyalty bonuses based on their roles and qualifying service years. The Company accounts for this program in accordance with ASC 710, Compensation, and accrues for the bonus payments on a straight-line basis over the service period, and has made an accounting policy election to account for forfeitures as they occur. In 2025, the Company discontinued the program and made the final payment in August 2025.

Effective January 1, 2023, the Company implemented a deferred compensation plan for non-partner employees holding the title of Director. The plan provides annual awards, the value of which is determined at the discretion of the Board of Directors. Payments are contingent upon the continued employment of participants during the five-year payment period. The Company accounts for this plan in accordance with ASC 710, whereby it accrues deferred compensation liabilities over the payment period. Liabilities are accrued using on a straight-line basis over the service period and are adjusted for changes, such as participant terminations. Cash payments are recorded annually as a reduction of the liability.

Liabilities for these programs are recorded in current and non-current liabilities, depending on the anticipated timing of payment.

Incentive Compensation

Certain client-serving individuals are eligible for variable incentive compensation arrangements. These generally represent a fixed bonus percentage based upon revenue collected. In some cases, these individuals are subject to minimum guaranteed payments. The Company accrues for such arrangements on a monthly basis as amounts are earned. These costs are recorded as cost of services in the consolidated statements of operations.

Equity-Based Compensation

Equity-based compensation is accounted for as an expense in accordance with ASC Topic 718, Stock Compensation, which requires compensation cost for the grant-date fair value of equity-based awards to be recognized over the requisite service period. The Company uses the straight-line method to amortize all stock awards granted over the requisite service period of the award. The Company accounts for forfeitures when they occur, and any compensation expense previously recognized on unvested equity-based awards is reversed when forfeited.

The fair value of restricted stock units and restricted Class X Aggregator Units is based on the fair value of the Class A common stock at the time of grant.

The fair value of LTIP Units is estimated using a Monte Carlo simulation approach. These require management to make assumptions on the grant date, including the expected term of the award, the expected volatility of the Company’s Class A common stock calculated based on a period of time generally commensurate with the expected term of the award, risk-free interest rates, expected dividend yields of the Company’s Class A common stock, and the probability of achieving the hurdle amount.

See Note 14 for a discussion of the Company’s equity-based compensation plans and awards.

Profits Interest

Prior to the IPO, the board of directors of Andersen Tax Holdings LLC was authorized to grant awards that qualify as profits interests for U.S. federal income tax purposes in accordance with the Company’s governing documents. Certain entities were awarded profits interests in the Company on behalf of certain executives and advisers and are considered related parties. These interests grant the recipients the right to certain cash distributions, based upon a percentage of license fees collected from certain trademarks of the Company. A profits interest award is accounted for based on its substance. A

profits interest award that is in substance a profit-sharing arrangement or performance bonus would generally not be within the scope of the stock-based compensation guidance under ASC 718, and would be accounted for under the guidance for deferred compensation plans under ASC 710 similar to a cash bonus. However, if the arrangement has characteristics more akin to the risks and rewards of equity ownership, the arrangement would be accounted for under stock-based compensation guidance.

The Company analyzes awards granted to recipients at the time they are granted or modified. The Company accounts for profits interest awards under ASC 710 as a cash bonus plan with performance conditions. The Company accrues compensation expense when it determines payment is probable and estimable, which is when the license fees are collected. The Company records the corresponding profits interest liability within other current liabilities or other liabilities on the consolidated balance sheets based on the estimated distribution date.

Revenue Recognition

Revenue primarily consists of professional service fees derived from tax, valuation, financial advisory and related consulting services. The Company recognizes revenue as the promised services are provided, in an amount that reflects the consideration which the Company expects to receive in exchange for those services. The Company recognizes revenue following a five-step model: (i) identify contract(s) with a client; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenues when (or as) the Company satisfies the performance obligation(s). For each performance obligation identified, the Company determines at contract inception whether it satisfies the performance obligation over time or satisfies the performance obligation at a point in time. If the Company does not satisfy a performance obligation over time, the performance obligation is satisfied at a point in time. In most of the Company’s client arrangements, the period between client payment and transfer of control of the service is expected to be one year or less. Therefore, the Company has elected the practical expedient to not adjust the amount of consideration for the effects of a significant financing component.

Clients are generally billed for services using an hourly rate. Certain customers may receive discounts and price concessions, which are accounted for as variable consideration in determining the transaction price.

The Company records revenue over time as services are performed and time and materials are charged to specific client codes. Contractual billings represent amounts that correspond directly with the value provided to the client (e.g., the number of hours worked at contractually agreed-upon rates), and revenue is recognized as amounts become billable in accordance with contractual terms.

Certain of these contracts are contingent upon achieving contractual targets to collect the fee. Due to the uncertainty of the outcome and the probability that a change in estimate would result in a significant reversal of revenue, the Company has applied a constraint on recording contingent revenue. Revenue is recognized when the constraint has been lifted, which is the date when the contractual target has been achieved, or cash has been collected.

Reimbursable expenses that are billed to clients, primarily relating to travel and out-of-pocket expenses incurred in connection with client engagements, are included in revenue, and an equivalent amount of reimbursable expenses is included in costs of services in the period in which the expense is incurred.

The timing of billings and cash collections may result in unbilled services, accounts receivable and deferred revenue on the consolidated balance sheet. Amounts are billed either at periodic intervals (e.g., monthly or quarterly) or upon the achievement of contractual milestones. Payments received in advance of the client receiving a benefit is a contract liability and is presented as deferred revenue in the consolidated balance sheet. Deferred revenue that is expected to be recognized as revenue within one year is recorded as the current portion of deferred revenue and the remaining portion is recorded as non-current deferred revenue. The Company does not have non-current deferred revenue at December 31, 2025 and 2024. Other contract balances consist of accounts receivable (including both billed and unbilled services), net of allowance for credit losses.

Operating Expenses

Cost of Services

Cost of services primarily consist of direct expenses related to the production of deliverables under client assignments. This includes personnel costs for revenue-generating personnel, such as wages, benefits, equity-based compensation, incentive compensation, and sub-consultant costs, software costs, and an allocation of non-personnel costs such as occupancy costs.

Sales, General and Administrative

Sales, general and administrative expenses primarily consist of personnel costs such as wages, benefits, equity-based compensation, and incentive compensation related to support and administrative functions, and non-personnel costs such as professional fees, business development, occupancy, advertising, recruiting, and training costs. Advertising costs were immaterial during the years ended December 31, 2025, 2024 and 2023.

Depreciation and Amortization

Depreciation and amortization expenses primarily consist of depreciation and amortization of the Company’s property and equipment, capitalized software, and acquired intangible assets.

Income Taxes

Andersen Group Inc. is taxed as a C corporation and is subject to U.S. federal, state and local income taxes on its share of allocable partnership income. Andersen Group Inc.’s sole material asset is its ownership in AT Umbrella LLC, which is a limited liability company that is taxed as a partnership for U.S. federal and certain state and local income tax purposes. AT Umbrella LLC’s allocable share of taxable income and related tax credits, if any, are passed through to its members, including Andersen Group Inc., and are included in the members’ tax returns.

In any period in which Andersen Group Inc. acquires additional units of AT Umbrella LLC by means of an exchange transaction, Andersen Group Inc. records the related income tax effects as an adjustment to equity.

The Company accounts for income taxes in accordance with the asset and liability approach for financial accounting and reporting, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, the Company determines deferred tax assets and liabilities on the basis of the differences between the financial statement and tax bases of assets and liabilities by using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date.

The Company recognizes deferred tax assets to the extent that the Company believes that these assets are more likely than not to be realized. In making such a determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If the Company determines that it would be able to realize deferred taxes in the future in excess of their net recorded amount, the Company would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.

The Company records uncertain tax positions in accordance with ASC 740, Accounting for Income Taxes on the basis of a two-step process in which (1) the Company determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, the Company recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority.

The Company recognizes interest and penalties related to unrecognized tax benefits as a component of income tax expense in the consolidated statements of operations.

The Company’s policy for global intangible low taxed income (“GILTI”) is to treat as a period cost when incurred.

Amounts Payable to Related Parties Pursuant to Tax Receivable Agreement

In connection with the IPO and Reorganization Transactions, the Company entered into the TRA with certain pre-IPO owners that provides for the payment to certain holders of Class X Umbrella Units who are or may become parties to the TRA from time to time 85% of the amount of cash savings, if any, in U.S. federal, state and local income tax or franchise tax that the Company realizes or is deemed to realize (determined by using assumptions regarding combined state and local income tax rates) as a result of (i) any increase in tax basis in the assets of AT Umbrella LLC and its flow-through subsidiaries resulting from purchases of Class X Umbrella Units from such Class X Umbrella Unit holders with the proceeds of this offering or resulting from exchanges of Class X Umbrella Units for at Andersen Group Inc.’s election, shares of Class A common stock or cash in the future; and (ii) certain other tax benefits related to entering into the TRA, including tax benefits attributable to payments that are made under the TRA. The TRA will make certain simplifying assumptions regarding the determination of the cash savings that are realized or are deemed to realize from the covered tax attributes, which may result in payments pursuant to the TRA in excess of those that would result if such assumptions were not made. No party to the TRA will reimburse the Company for any payments previously made if such basis increases or other benefits are subsequently disallowed, except that excess payments made to the TRA parties will be netted against future payments that would otherwise be made under the TRA, if any, after determination of such excess. The Company accounts for amounts payable under the TRA in accordance with ASC Topic 450, Contingencies. As such, subsequent changes in the fair value of the TRA liability between reporting periods are recognized in the consolidated statement of operations.

The Company has not yet incurred a liability in connection with the TRA.

Loss per Share

Basic loss per share is calculated by dividing the net loss by the weighted-average number of shares of the Company’s Class A common stock outstanding for the period, without consideration for potential dilutive shares of common stock. Shares of Class B common stock and RSUs are not entitled to receive any distributions or dividends and are therefore excluded from this presentation since they are not participating securities. The Company calculates diluted loss per share using the treasury stock method for RSUs and the if-converted method for redeemable Class X Umbrella Units and LTIP Units. For the period following the IPO and Reorganization Transactions through December 31, 2025, 98,294,464 Class X Umbrella Units were considered dilutive and have been included in the calculation of diluted net loss per share.

The Company did not include earnings per unit for the pre-IPO period as part of its financial statements. All earnings prior to December 18, 2025, the completion date of the IPO, were entirely allocable to the redeemable noncontrolling interest and, as a result, earnings per share information is not applicable for reporting periods prior to this date. Consequently, only earnings per share for net loss for periods including and subsequent to December 18, 2025 are presented.

Recently Issued Accounting Pronouncements

Changes to U.S. GAAP are established by the FASB in the form of Accounting Standards Updates ("ASUs") to the FASB Accounting Standards Codification. ASUs issued which are not specifically listed below were assessed and have already been adopted in a prior period or determined to be either not applicable or are not expected to have a material impact on the Company’s consolidated financial statements and related disclosures.

Recent Accounting Pronouncements Not Yet Adopted

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures (“ASU 2023-09”), which requires disclosure of disaggregated income taxes paid, prescribes standard categories for the components of the effective tax rate reconciliation, and modifies other income tax-related disclosures. Early adoption is permitted. Upon adoption, the guidance may be applied prospectively or retrospectively. For public business entities, the amendments are effective for fiscal years beginning after December 15, 2024. For entities other than public business entities, the amendments are effective for annual periods beginning after December 15, 2025. As an emerging growth company, the Company has elected the extended transition period for complying with new or revised accounting standards and this ASU has not yet been adopted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures.

In November 2024, the FASB issued ASU 2024-03, Income Statement (Topic 220): Reporting Comprehensive Income - Expense Disaggregation Disclosures, Disaggregation of Income Statement Expenses ("ASU 2024-03"), which requires public business entities to disclose, in interim and annual reporting periods, additional information about certain expenses in the consolidated financial statements. The amendments in this ASU will be effective for annual periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Early adoption is permitted and is effective on either a prospective basis or retrospective basis. The Company is currently evaluating the potential impact that the adoption of this standard will have on its consolidated financial statements.

In May 2025, the FASB issued ASU No. 2025-03, Business Combinations (Topic 805) and Consolidation (Topic 810): Determining the Accounting Acquirer in the Acquisition of a Variable Interest Entity (“VIE”), which provides clarifying guidance on determining the accounting acquirer in certain transactions involving VIEs. The update aims to improve consistency and comparability in financial reporting. The guidance will be effective for all entities for annual periods beginning after December 15, 2026, including interim periods within those annual periods. Early adoption is permitted. Upon adoption, the guidance will be applied prospectively. The Company is currently evaluating the potential impact that the adoption of this standard will have on its consolidated financial statements.

In July 2025, the FASB issued ASU No. 2025-05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets, which added a practical expedient that assumes that current conditions as of the balance sheet date do not change for the remaining life of the asset when estimating expected credit losses for current accounts receivable and current contract assets. The guidance is effective for all entities for annual periods beginning after December 15, 2025. The Company plans to adopt this ASU on the effective date and does not expect it to have a material impact on its consolidated financial statements.

In September 2025, the FASB issued ASU No. 2025-06, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Targeted Improvements in Accounting for Internal-Use Software, which replaced the “project stage” model with a principles-based framework for cost recognition and capitalization of internal-use software. The update requires companies to capitalize internal-use software costs when management authorizes and commits funding for the software project and when it is probable the project will be completed and the software will be used to perform the function intended. The guidance will be effective for all entities for annual periods beginning after December 15, 2027, including interim periods within those annual periods. Early adoption is permitted. Upon adoption, the guidance may be applied prospectively or retrospectively. The Company is currently evaluating the potential impact that the adoption of this standard will have on its consolidated financial statements.

In September 2025, the FASB issued ASU No. 2025-07, Derivatives and Hedging (Topic 815) and Revenue from Contracts with Customers (Topic 606): Derivatives Scope Refinements and Scope Clarification for Share-Based Noncash Consideration From a Customer in a Revenue Contract. ASU 2025-07 introduces guidance for applying derivative accounting to contracts that include features tied to the operations or activities of one of the parties to the contract. It also aims to reduce diversity in how share-based payments are accounted for in revenue contracts. ASU 2025-07 will be effective for the annual periods beginning after December 15, 2026 with early adoption permitted. The Company is currently evaluating the potential impact that the adoption of this standard will have on its consolidated financial statements.

In December 2025, the FASB issued ASU 2025-11, Interim Reporting (Topic 270) Narrow- Scope Improvements. The amendments in this ASU do not change the fundamental nature of interim reporting or expand or reduce current interim disclosure. The amendments in this ASU clarify the guidance in ASC Topic 270 by providing a comprehensive list of required interim disclosures and codifying a disclosure principle that requires the Company to disclose events and changes that occur after the end of the most recent annual reporting period that have a material impact on its consolidated financial statements. The amendments in this ASU are effective for interim periods within annual reporting periods beginning after December 15, 2027. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements.

In December 2025, the FASB issued ASU 2025-12, Codification Improvements (Topic 815). The amendments in this ASU update the FASB Accounting Standards Codification for a broad range of Topics arising from technical corrections, unintended application of the Codification, clarifications, and other minor improvements. The amendments in this ASU are effective for all entities for annual periods beginning after December 15, 2026, and interim periods within those annual

periods. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements.