SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	The accompanying interim condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) regarding interim financial reporting, and do not include all disclosures, including certain notes, required by U.S. GAAP on an annual reporting basis. These interim condensed consolidated financial statements are unaudited and, in the opinion of management, reflect all normal recurring adjustments necessary to fairly present the financial position, results of operations, cash flows, and change in equity for the periods presented. Results for the periods presented are not necessarily indicative of the results that may be expected for any subsequent period. These unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements and notes as of and for the year ended December 31, 2020 as disclosed in the Company’s prospectus, dated November 9, 2021, filed with the Securities and Exchange Commission (“SEC”) in accordance with Rule 424(b) of the Securities Act on November 12, 2021 (the “Prospectus”) in connection with the Company’s initial public offering (“IPO”).
Basis of Consolidation	The Company consolidates entities that are controlled as a result of having a controlling financial interest in those entities. Intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Accounting estimates are an integral part of the consolidated financial statements. These estimates require the use of judgments and assumptions that may affect the reported amounts of assets, liabilities, and expenses in the period presented. The Company believes that the accounting estimates and related assumptions employed by the Company are appropriate and the resulting balances are reasonable under the circumstances. However, due to the inherent uncertainties involved in making estimates, the actual results could differ from the original estimates, requiring adjustments to these balances in future periods.
Cash and Cash Equivalents	Cash and cash equivalents include cash on hand, cash in banks, and money market funds with maturities of three months or less. All short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates are classified as cash equivalents.
Restricted Cash	Cash and cash equivalents that are restricted as to withdrawal or use under the terms of certain contractual agreements are recorded in “Other current assets” and “Other assets” on the Company’s Condensed Consolidated Balance Sheets.
Inventory and Inventory Valuation	Inventory is stated at the lower of cost or net realizable value (“LCNRV”) and consists of raw materials, work-in-progress, and finished goods. The Company primarily computes cost using standard cost, which approximates cost on the first-in, first-out (“FIFO”) basis. Net realizable value (“NRV”) is the estimated selling price of inventory in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The Company assesses the valuation of inventory and periodically adjusts its value for estimated excess and obsolete inventory based upon expectations of future demand and market conditions, as well as damaged or otherwise impaired goods.
Cost of Vehicle Revenue	Cost of vehicle revenue includes direct parts, material and labor costs, manufacturing overhead (e.g., depreciation of machinery and tooling), inbound shipping and logistics costs, and reserves for estimated warranty costs. Cost of vehicle revenue also includes adjustments to write down the carrying value of inventory when it exceeds its estimated NRV and to provide for on-hand inventory that is either obsolete or in excess of forecasted demand.
Fair Value Measurement	A three-level valuation hierarchy, based upon observable and unobservable inputs, is used for fair value measurements. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect market assumptions based on the best evidence available. These two types of inputs create the following fair value hierarchy: •Level 1 – Quoted prices for identical instruments in active markets •Level 2 – Quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations whose significant inputs are observable •Level 3 – Instruments with model-derived valuations whose significant inputs are unobservable
Research and Development Costs	Research and development (“R&D”) costs consist primarily of personnel costs for teams in engineering and research, prototyping expenses, contract and professional services, amortized equipment costs, and allocation of indirect costs. R&D costs are expensed as incurred.
Marketing, Advertising, and Promotion	Marketing, advertising, and promotion costs are included as part of Selling, general, and administrative expense in the Conde nsed C onsolidated S tatement of O perations, and such costs are expensed as they are incurred.
Concentration of Risk	Counterparty Credit Risk Financial instruments that potentially subject the Company to concentration of counterparty credit risk consist of cash and cash equivalents, deposits, and loans. As of December 31, 2020 and September 30, 2021, all of the Company’s cash and cash equivalents were placed at financial institutions that management believes are of high credit quality. These amounts are typically in excess of insured limits. Supply Risk The Company is subject to risks related to its dependence on its suppliers, the majority of which are single source providers of parts or components for the Company’s products. Any inability of the Company’s suppliers to deliver necessary product components, including semiconductors, at timing, prices, quality, and volumes that are acceptable to the Company could have a material and adverse impact on Rivian’s business, growth prospects, and financial and operating results. The Company’s manufacturing facility in Normal, Illinois (the “Normal Factory”) is operational, and Rivian is continuing to invest in the Normal Factory. The Company’s ability to continue to prepare for and sustain production depends, among other things, on the readiness and solvency of suppliers and vendors through all macroeconomic factors, including factors resulting from the COVID-19 pandemic.
Accounting Pronouncements Recently Adopted	ACCOUNTING PRONOUNCEMENTS RECENTLY ADOPTEDIn August 2020, the FASB issued Accounting Standards Update (“ASU”) 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity. The ASU simplifies (i) the accounting for convertible financing instruments issued, including preferred stock, (ii) the derivatives scope exception for contracts in an entity’s own equity, and (iii) the calculation of earnings per share. Early adoption by private companies is permissible, and the Company elected to early adopt the new accounting standard on January 1, 2021. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements and disclosures.
Property, Plant and Equipment, Net	Property, plant, and equipment are recorded at cost, net of accumulated depreciation and impairments. Costs incurred for routine maintenance and repair are expensed when incurred. The Company capitalizes certain qualified costs incurred in connection with the development of internal-use software. Costs incurred during the application development stage are evaluated to determine whether the costs meet the criteria for capitalization. Costs related to preliminary project activities and post implementation activities, including maintenance, are expensed as incurred.Property, plant, and equipment are primarily depreciated using the straight-line method over the estimated useful life of the asset. Leasehold improvements are amortized over the period of lease or the life of the asset, whichever is shorter, using the straight-line method. Capitalized costs related to internal-use software are amortized using the straight-line method over the estimated useful life of the asset. Land is not depreciated.
Fair Value Assumptions	The Company estimates the fair value of each stock option award using a Black-Scholes option pricing model.Prior to the three months ended September 30, 2021, the fair value of RSUs was measured on the grant date based on an independent appraisal of the fair market value of the Company’s common stock. The independent appraisal used a market approach with an adjustment for lack of marketability given that the shares underlying the awards were not publicly traded (see Note 14 “Subsequent Events” for updates concerning the Company’s November 2021 IPO). This assessment required complex and subjective judgments regarding the Company’s projected financial and operating results, business risks, liquidity of ordinary shares, operating history, and prospects.In light of the difference between the fair value of a share of the Company’s common stock applicable to stock options and RSUs granted during the three months ended September 30, 2021, based on an independent appraisal, and initial information received in estimation of the Company’s IPO price range as well as the proximity of such grants to the IPO, the Company established the fair value of a share of the Company’s common stock applicable to stock options and RSUs granted from July 20, 2021 onward using a straight-line interpolation from the July 20, 2021 fair value estimated using an independent appraisal to the midpoint of the initial price range in order to calculate unrecognized stock-based compensation expense (see Note 14 “Subsequent Events” for updates concerning the Company’s November 2021 IPO).
Commitments and Contingencies	Liabilities for loss contingencies arising from claims, assessments, litigation, fines and penalties, and other sources are recorded when it is probable that a liability has been incurred and the related amount can be reasonably estimated. If an amount within the range of loss appears at the time to be a better estimate than any other amount within the range, that amount is accrued. When no amount within the range is a better estimate than any other amount, the minimum amount in the range is accrued. If a loss is reasonably possible and the loss or range of loss cannot be reasonably estimated, the Company discloses the possible loss or states that such an estimate cannot be made.
Net Loss Per Share	The Company’s basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period after allocating losses to equity awards deemed to be participating securities pursuant to the two-class method. Diluted net loss per share is calculated by dividing the net loss by the weighted-average shares outstanding assuming dilution. Specifically, diluted net loss per share is computed by giving effect to all potential shares of common stock, including stock options, unvested RSUs, stock warrants, and convertible debt to the extent dilutive.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

9 Months Ended

Sep. 30, 2021

The accompanying interim condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) regarding interim financial reporting, and do not include all disclosures, including certain notes, required by U.S. GAAP on an annual reporting basis. These interim condensed consolidated financial statements are unaudited and, in the opinion of management, reflect all normal recurring adjustments necessary to fairly present the financial position, results of operations, cash flows, and change in equity for the periods presented. Results for the periods presented are not necessarily indicative of the results that may be expected for any subsequent period. These unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements and notes as of and for the year ended December 31, 2020 as disclosed in the Company’s prospectus, dated November 9, 2021, filed with the Securities and Exchange Commission (“SEC”) in accordance with Rule 424(b) of the Securities Act on November 12, 2021 (the “Prospectus”) in connection with the Company’s initial public offering (“IPO”).

Basis of Consolidation

The Company consolidates entities that are controlled as a result of having a controlling financial interest in those entities. Intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

Accounting estimates are an integral part of the consolidated financial statements. These estimates require the use of judgments and assumptions that may affect the reported amounts of assets, liabilities, and expenses in the period presented. The Company believes that the accounting estimates and related assumptions employed by the Company are appropriate and the resulting balances are reasonable under the circumstances. However, due to the inherent uncertainties involved in making estimates, the actual results could differ from the original estimates, requiring adjustments to these balances in future periods.

Cash and Cash Equivalents

Cash and cash equivalents include cash on hand, cash in banks, and money market funds with maturities of three months or less. All short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates are classified as cash equivalents.

Restricted Cash

Cash and cash equivalents that are restricted as to withdrawal or use under the terms of certain contractual agreements are recorded in “Other current assets” and “Other assets” on the Company’s Condensed Consolidated Balance Sheets.

Inventory and Inventory Valuation

Inventory is stated at the lower of cost or net realizable value (“LCNRV”) and consists of raw materials, work-in-progress, and finished goods. The Company primarily computes cost using standard cost, which approximates cost on the first-in, first-out (“FIFO”) basis. Net realizable value (“NRV”) is the estimated selling price of inventory in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The Company assesses the valuation of inventory and periodically adjusts its value for estimated excess and obsolete inventory based upon expectations of future demand and market conditions, as well as damaged or otherwise impaired goods.

Cost of Vehicle Revenue

Cost of vehicle revenue includes direct parts, material and labor costs, manufacturing overhead (e.g., depreciation of machinery and tooling), inbound shipping and logistics costs, and reserves for estimated warranty costs. Cost of vehicle revenue also includes adjustments to write down the carrying value of inventory when it exceeds its estimated NRV and to provide for on-hand inventory that is either obsolete or in excess of forecasted demand.

Fair Value Measurement

A three-level valuation hierarchy, based upon observable and unobservable inputs, is used for fair value measurements. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect market assumptions based on the best evidence available. These two types of inputs create the following fair value hierarchy:

•Level 1 – Quoted prices for identical instruments in active markets

•Level 2 – Quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations whose significant inputs are observable

•Level 3 – Instruments with model-derived valuations whose significant inputs are unobservable

Research and Development Costs

Research and development (“R&D”) costs consist primarily of personnel costs for teams in engineering and research, prototyping expenses, contract and professional services, amortized equipment costs, and allocation of indirect costs. R&D costs are expensed as incurred.

Marketing, Advertising, and Promotion

Marketing, advertising, and promotion costs are included as part of Selling, general, and administrative expense in the Conde nsed C onsolidated S tatement of O perations, and such costs are expensed as they are incurred.

Concentration of Risk

Counterparty Credit Risk

Financial instruments that potentially subject the Company to concentration of counterparty credit risk consist of cash and cash equivalents, deposits, and loans. As of December 31, 2020 and September 30, 2021, all of the Company’s cash and cash equivalents were placed at financial institutions that management believes are of high credit quality. These amounts are typically in excess of insured limits.

Supply Risk

The Company is subject to risks related to its dependence on its suppliers, the majority of which are single source providers of parts or components for the Company’s products. Any inability of the Company’s suppliers to deliver necessary product components, including semiconductors, at timing, prices, quality, and volumes that are acceptable to the Company could have a material and adverse impact on Rivian’s business, growth prospects, and financial and operating results.

The Company’s manufacturing facility in Normal, Illinois (the “Normal Factory”) is operational, and Rivian is continuing to invest in the Normal Factory. The Company’s ability to continue to prepare for and sustain production depends, among other things, on the readiness and solvency of suppliers and vendors through all macroeconomic factors, including factors resulting from the COVID-19 pandemic.

Accounting Pronouncements Recently Adopted

ACCOUNTING PRONOUNCEMENTS RECENTLY ADOPTEDIn August 2020, the FASB issued Accounting Standards Update (“ASU”) 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity. The ASU simplifies (i) the accounting for convertible financing instruments issued, including preferred stock, (ii) the derivatives scope exception for contracts in an entity’s own equity, and (iii) the calculation of earnings per share. Early adoption by private companies is permissible, and the Company elected to early adopt the new accounting standard on January 1, 2021. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements and disclosures.

Property, Plant and Equipment, Net

Property, plant, and equipment are recorded at cost, net of accumulated depreciation and impairments. Costs incurred for routine maintenance and repair are expensed when incurred. The Company capitalizes certain qualified costs incurred in connection with the development of internal-use software. Costs incurred during the application development stage are evaluated to determine whether the costs meet the criteria for capitalization. Costs related to preliminary project activities and post implementation activities, including maintenance, are expensed as incurred.Property, plant, and equipment are primarily depreciated using the straight-line method over the estimated useful life of the asset. Leasehold improvements are amortized over the period of lease or the life of the asset, whichever is shorter, using the straight-line method. Capitalized costs related to internal-use software are amortized using the straight-line method over the estimated useful life of the asset. Land is not depreciated.

Fair Value Assumptions

The Company estimates the fair value of each stock option award using a Black-Scholes option pricing model.Prior to the three months ended September 30, 2021, the fair value of RSUs was measured on the grant date based on an independent appraisal of the fair market value of the Company’s common stock. The independent appraisal used a market approach with an adjustment for lack of marketability given that the shares underlying the awards were not publicly traded (see Note 14 “Subsequent Events” for updates concerning the Company’s November 2021 IPO). This assessment required complex and subjective judgments regarding the Company’s projected financial and operating results, business risks, liquidity of ordinary shares, operating history, and prospects.In light of the difference between the fair value of a share of the Company’s common stock applicable to stock options and RSUs granted during the three months ended September 30, 2021, based on an independent appraisal, and initial information received in estimation of the Company’s IPO price range as well as the proximity of such grants to the IPO, the Company established the fair value of a share of the Company’s common stock applicable to stock options and RSUs granted from July 20, 2021 onward using a straight-line interpolation from the July 20, 2021 fair value estimated using an independent appraisal to the midpoint of the initial price range in order to calculate unrecognized stock-based compensation expense (see Note 14 “Subsequent Events” for updates concerning the Company’s November 2021 IPO).

Commitments and Contingencies

Liabilities for loss contingencies arising from claims, assessments, litigation, fines and penalties, and other sources are recorded when it is probable that a liability has been incurred and the related amount can be reasonably estimated. If an amount within the range of loss appears at the time to be a better estimate than any other amount within the range, that amount is accrued. When no amount within the range is a better estimate than any other amount, the minimum amount in the range is accrued. If a loss is reasonably possible and the loss or range of loss cannot be reasonably estimated, the Company discloses the possible loss or states that such an estimate cannot be made.

Net Loss Per Share

The Company’s basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period after allocating losses to equity awards deemed to be participating securities pursuant to the two-class method. Diluted net loss per share is calculated by dividing the net loss by the weighted-average shares outstanding assuming dilution. Specifically, diluted net loss per share is computed by giving effect to all potential shares of common stock, including stock options, unvested RSUs, stock warrants, and convertible debt to the extent dilutive.