The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make certain estimates, judgments and assumptions that affect the reported amounts of assets and liabilities and the related disclosures at the date of the financial statements, as well as the reported amounts of revenues and expenses during the periods presented. We base our estimates on historical experience and other relevant assumptions that we believe to be reasonable under the circumstances. Estimates are used in several areas including, but not limited to, estimates of progress to date for certain performance obligations and the transaction price for certain contracts with customers, share-based compensation, the provision for income taxes, including related reserves, and goodwill, among others. These estimates generally involve complex issues and require judgments, involve the analysis of historical results and prediction of future trends, can require extended periods of time to resolve and are subject to change from period to period. Actual results may differ materially from management’s estimates.

In our opinion, the accompanying unaudited condensed consolidated financial statements have been prepared in accordance with GAAP for interim financial information. These unaudited condensed consolidated financial statements include all adjustments necessary to fairly state the financial position and the results of our operations and cash flows for interim periods in accordance with GAAP. All such adjustments are of a normal, recurring nature. Interim-period results are not necessarily indicative of results of operations or cash flows for a full year or any subsequent interim period.

The accompanying unaudited condensed consolidated financial statements should be read in conjunction with our audited financial statements and notes included in our Annual Report on Form 10-K for the year ended December 31, 2020 filed with the SEC on February 24, 2021.

We are required to maintain certain balances under lease arrangements for some of our property and facility leases. We had restricted cash of $2.1 million as of March 31, 2021 and December 31, 2020.

We determine if an arrangement contains a lease at inception. We have operating lease agreements for the laboratory and office facilities that we occupy, as well as server space. Operating lease right-of-use (“ROU”) assets and operating lease liabilities are recognized at the date the underlying asset becomes available for our use and are based on the present value of the future minimum lease payments over the lease term. ROU assets also include any initial direct costs incurred and any lease payments made at or before the lease commencement date, less lease incentives received. As our leases generally do not provide an implicit interest rate, the present value of our future minimum lease payments is determined using our incremental borrowing rate. This rate is an estimate of the collateralized borrowing rate we would incur on our future lease payments over a similar term and is based on the information available to us at the lease commencement date, or as of January 1, 2020 for commenced leases that existed as of our adoption of the new lease standard.

Certain of our leases contain options to extend or terminate the lease; lease terms are adjusted for these options only when it is reasonably certain we will exercise these options. Our lease agreements do not contain residual value guarantees or covenants.

We have made a policy election regarding our real estate leases not to separate nonlease components from lease components, to the extent they are fixed. Nonlease components that are not fixed are expensed as incurred as variable lease expense. Our leases for laboratory and office facilities typically include variable nonlease components, such as common-area maintenance costs. We have also elected not to record on the balance sheet a lease that has a lease term of twelve months or less and does not contain a purchase option that we are reasonably certain to exercise.

Lease expense is recognized on a straight-line basis over the terms of the leases. Incentives granted under our facilities leases, including rent holidays, are recognized as adjustments to lease expense on a straight-line basis over the terms of the leases.

We are subject to a concentration of risk from a limited number of suppliers, or in some cases single suppliers, for some of our laboratory instruments and materials. This risk is managed by targeting a quantity of surplus stock.

Cash, cash equivalents and marketable securities are financial instruments that potentially subject us to concentrations of credit risk. We invest in money market funds, United States (“U.S.”) government debt securities, U.S. government agency securities, commercial paper and corporate bonds with high-quality accredited financial institutions.

Significant customers are those that represent more than 10% of our total revenue or accounts receivable, net balances for the periods and as of each balance sheet date presented, respectively. Revenue from these customers reflects their purchase of our products and services and our collaboration efforts with Genentech.

For each significant customer, revenue as a percentage of total revenue for the periods presented and accounts receivable, net as a percentage of total accounts receivable, net as of the dates presented were as follows:

	Revenue		Accounts Receivable, Net
	Three Months Ended March 31,		March 31,	December 31,
	2021	2020	2021	2020
Customer A	*%	*%	*%		19.1	%
Customer B	10.4	*	17.8	12.2
Customer D	10.0	*	19.4	*
Customer E	*	*	17.8	*
Genentech, Inc. and Roche Group	42.1	54.4	*	*
* less than 10%

We recognize revenue in accordance with Accounting Standards Codification (“ASC”) Topic 606 (“ASC 606”), Revenue from Contracts with Customers. Under ASC 606, for all revenue-generating contracts, we perform the following steps to determine the amount of revenue to be recognized: (1) identify the contract or contracts; (2) determine whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (3) measure the transaction price, including the constraint on variable consideration; (4) allocate the transaction price to the performance obligations based on estimated selling prices; and (5) recognize revenue when (or as) we satisfy each performance obligation. The following is a summary of the application of the respective model to each of our revenue classifications.

Our revenue is generated from immunosequencing (“sequencing”) products and services (“sequencing revenue”) and from regulatory or development support services leveraging our immune medicine platform (“development revenue”). When revenue generating contracts have elements of both sequencing revenue and development revenue, we classify revenue based on the nature of the performance obligation and the allocated transaction price.

Sequencing revenue reflects the amounts generated from providing sequencing services and testing through our clonoSEQ and immunoSEQ products and services to our clinical and research customers, respectively.

For clinical customers, we derive revenues from providing our clonoSEQ report to ordering physicians, and we bill and receive payments from medical institutions and commercial and government third-party payors. In these transactions, we have identified one performance obligation: the delivery of a clonoSEQ report. As payment from the respective payors may vary based on the various reimbursement rates and patient responsibilities, we consider the transaction price to be variable and record an estimate of the transaction price, subject to the constraint for variable consideration, as revenue at the time of delivery. The estimate of transaction price is based on historical and expected reimbursement rates with the various payors, which are monitored in subsequent periods and adjusted as necessary based on actual collection experience.

For our clonoSEQ coverage under Medicare, we bill an episode of treatment when we deliver the first eligible test results. This billing contemplates all necessary tests required during a patient’s treatment cycle, which is currently estimated at approximately four tests per patient, including the initial sequence identification test. Revenue recognition commences at the time the initial billable test result is delivered and is based upon cumulative tests delivered to date. We estimate the number of tests we expect to deliver over a patient’s treatment cycle based on historical testing frequencies for patients by indication. These estimates are subject to change as we develop more information about utilization over time. Any unrecognized revenue from the initial billable test is recorded as deferred revenue and is recognized as we deliver the remaining tests in a patient’s treatment cycle or when it becomes remote that a patient will receive additional testing and we have not delivered our estimate of total tests.

For research customers, contracts typically include an amount billed in advance of services (“upfront”) and subsequent billings as sample results are delivered to the customer. Upfront amounts received are recorded as deferred revenue, which we recognize as revenue upon satisfaction of performance obligations. We have identified two typical performance obligations under the terms of our research service contracts: sequencing services and related data analysis. We recognize revenue for both identified performance obligations as sample results are delivered to the customer.

We derive revenue by providing services through development agreements to biopharmaceutical customers who seek access to our immune medicine platform technologies. We generate revenues from the delivery of professional support activities pertaining to the use of immunoSEQ and our minimal residual disease (“MRD”) product in the development of the respective customers’ initiatives. The transaction price for these contracts may consist of a combination of non-refundable upfront fees, separately priced sequencing fees, progress-based milestones and regulatory milestones. The development agreements may include single or multiple performance obligations, depending on the contract. For certain contracts, we may perform services to support the biopharmaceutical customers’ regulatory submissions as part of their registrational trials. These services include regulatory support pertaining to our technology intended to be utilized as part of the submission, development of analytical plans for our sequencing data, participation on joint research committees and assistance in completing a regulatory submission. Generally, these services are not distinct within the context of the contract and they are accounted for as a single performance obligation.

When sequencing services are separately priced customer options, we assess if a material right exists and, if not, the customer option to purchase additional sequencing services is not considered part of the contract. Except for any non-refundable upfront fees, the other forms of compensation represent variable consideration. Variable consideration related to progress-based and regulatory milestones is estimated using the most likely amount method, where variable consideration is constrained until it is probable that a significant reversal of cumulative revenue recognized will not occur. Progress milestones, such as the first sample result delivered or final patient enrollment in a customer trial, are customer dependent and are included in the transaction price when the respective milestone is probable of occurring. Milestone payments that are not within our customers’ control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. Determining whether regulatory milestone payments are probable is an area that requires significant judgment. In making this assessment, we evaluate scientific, clinical, regulatory and other risks, as well as the level of effort and investment required to achieve the respective milestone.

The primary method used to estimate standalone selling price for performance obligations is the adjusted market assessment approach. Using this approach, we evaluate the market in which we sell our services and estimate the price that a customer in that market would be willing to pay for our services. We recognize revenue using either an input or output measure of progress that faithfully depicts performance on a contract, depending on the contract. The measure used is dependent on the nature of the service to be provided in each contract. Selecting the measure of progress and estimating progress to date requires significant judgment.

We calculate basic net loss per share attributable to common shareholders by dividing the net loss attributable to common shareholders by the weighted-average number of shares of common stock outstanding for the period. The diluted net loss per share attributable to common shareholders is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period determined using the treasury stock method. For purposes of this calculation, common stock warrants, stock options and nonvested restricted stock units are considered common stock equivalents but have been excluded from the calculation of diluted net loss per share attributable to common shareholders, as their effect is anti-dilutive.