Summary of Significant Accounting Policies | Summary of Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles and include the accounts of iRhythm Technologies, Inc. and its wholly-owned subsidiary. All intercompany accounts and transactions have been eliminated. The financial statements of the Company’s subsidiary use the U.S. dollar as the functional currency. For all non-functional currency balances, the remeasurement of such balances to functional currency results in a foreign exchange transaction gain or loss, which is recorded in the consolidated statements of operations. Risks and Uncertainties COVID-19 As a result of the COVID-19 pandemic, the Company has experienced significant business disruptions, restrictions on its ability to travel, reduction in access to customers due to diverted resources at hospitals, and shortened business hours as governments institute prolonged shelter-in-place and/or self-quarantine mandates. Governmental mandates related to the COVID-19 pandemic have impacted, and is expected to continue to impact, Company personnel and personnel at third-party manufacturing facilities in the United States and other countries, and the availability or cost of materials, which could disrupt our supply chain and reduce margins. For instance, on or about March 16, 2020, the Health Officers of the counties of San Francisco (where the Company's headquarters is located), Santa Clara, San Mateo, Marin, Contra Costa and Alameda, where many employees are located, issued mandatory shelter-in-place orders and all employees transitioned to a remote work environment. The Company is also subject to orders in Southern California that temporarily shut down its manufacturing and distribution facilities in Cypress, California. For a limited number of employees who continue to support essential operations, including those at our manufacturing facilities, the Company has instituted protective equipment policies and, to the degree practical, social distancing measures to protect the safety of its employees. While the Company has continued to deliver its Zio service by operating with remote employees and essential employees on site, an extended implementation of these governmental mandates could further impact the Company's ability to effectively provide its Zio service, and could impede progress of all ongoing initiatives. Appropriate social distancing techniques and other measures at the Company's facilities have been implemented for the limited number of employees who have returned to work to support essential operations, and will not return until the risk to employee health has meaningfully diminishe d . While hospital systems and healthcare facilities shift their focus and resources to treating COVID-19 patients and combating the spread of the coronavirus, the Company has adapted its service to meet the immediate needs of physicians, customers, and patients and significantly increased the utilization of its home enrollment service which allows patients to receive and wear the single-use Zio device without going to a healthcare facility. Given the disruption in demand and an uncertain length of time to recovery, the Company adjusted its operating plan in the second quarter of 2020 by taking steps to reduce operating spend. These steps included eliminating or delaying spending on non-essential programs, reducing spend on travel and consulting, implementing a hiring freeze, furloughing approximately 5% of employees, conducting a layoff of approximately 2% of employees and implementing temporary pay reductions for our salaried workforce. From May 2020 to July 2020, the Company’s Chief Executive Officer, other named executive officers and other senior executives agreed to temporary base salary reductions and the Board of Directors agreed to a reduction in its fees until business and economic conditions improve. The Company also increased it’s bad debt reserve in anticipation of a potential increase in uncollectible co-payments from patients using the Zio Service. In August 2020, the Company reinstated furloughed employees, removed pay reductions for its salaried employees, and resumed hiring for most positions. The Company is continuously reviewing its liquidity and anticipated capital requirements in light of the significant uncertainty created by the COVID-19 pandemic. The Company believes it will have adequate liquidity over the next 12 months to operate its business and to meet its cash requirements. As of December 31, 2020, the Company is in compliance with its financial covenants in its debt agreement. On March 27, 2020, as a result of the COVID-19 pandemic, Congress enacted the Coronavirus Aid, Relief, and Economic Security Act (the "CARES Act") to support businesses during the COVID-19 pandemic, including deferment of the employer portion of certain payroll taxes, refundable payroll tax credits, and technical amendments to tax depreciation methods for qualified improvement property. The primary provisions of the CARES Act which are potentially applicable to us include: • certain amendments to the limitations on the deductibility of interest contained in Section 163(j) of the Internal Revenue Code of 1986, as amended, for taxable years beginning in 2019 and 2020; and • an allowance of net operating loss carrybacks for taxable years beginning in 2018 and before 2021. The Company did not qualify for the Paycheck Protection Program under the CARES Act due to the number of employees in our organization. The CARES Act did not have material impact on the Company’s overall consolidated financial statements. The ultimate impact of the COVID-19 pandemic is highly uncertain and subject to change. This impact is having a material, adverse impact on liquidity, capital resources, operations and business and those of the third parties on which the Company relies, and could worsen over time. The extent to which the COVID-19 pandemic impacts the Company’s results will depend on future developments, which are highly uncertain and cannot be predicted, including new information which may emerge concerning the severity of the COVID-19 pandemic and the actions to contain the COVID-19 pandemic or treat its impact, among others. The full extent of potential delays or impacts on the business, financial condition, cash flows and results of operations remains unknown. Additionally, while the potential economic impact brought by, and the duration of, the COVID-19 pandemic is difficult to assess or predict, the COVID-19 pandemic has resulted in, and may continue to result in, significant disruption of global financial markets, reducing the Company’s ability to raise additional capital through equity, equity-linked or debt financings, which could negatively impact short-term and long-term liquidity and the ability to operate on a timely basis, or at all. Furthermore, capital markets and economies worldwide have been negatively impacted by the COVID-19 pandemic, which may result in a period of regional, national, and global economic slowdown or regional, national, or global recessions that could curtail or delay demand for the Zio service as well as increase the risk of customer defaults or delays in payments. COVID-19 and the current financial, economic, and capital markets environment, and future developments in these and other areas present material uncertainty and risk with respect to the Company's performance, financial condition, volume of business, results of operations, and cash flows. Reimbursement Government payors may change their coverage and reimbursement policies, as well as payment amounts, in a way that would prevent or limit reimbursement for the Zio service, which would significantly harm the Company. Government and other third-party payors require the Company to report the service for which it is seeking reimbursement by using a Current Procedural Terminology (CPT), code-set maintained by the American Medical Association (AMA). For Zio XT, the Company had historically utilized temporary CPT codes (or Category III CPT codes), used for newly introduced technologies and specific to our category of diagnostic monitoring. The process to convert Category III CPT codes to Category I CPT codes is governed by the AMA and CMS. On October 25, 2019, the AMA’s CPT Editorial Panel established two new Category I CPT codes which are applicable to the Zio service and took effect on January 1, 2021. In August 2020, CMS published the Calendar Year 2021 Medicare Physician Fee Schedule Proposed Rule which proposed reimbursement for the Category I CPT codes that were higher than their associated Category III CPT codes. Following a comment period through October 2020, CMS published its Calendar Year 2021 Medicare Physician Fee Schedule Final Rule (the “Final Rule”) in December 2020. In the Final Rule, CMS chose not to finalize national pricing for four of the eight Category I CPT codes, 93241, 93243, 93245 and 93247 which include the CPT codes that the Company will primarily use to seek reimbursement for Zio XT. Determinations of which products or services will be reimbursed under Medicare can be developed at the national level through a national coverage determination (“NCD”) by CMS, or at the local level through a local coverage determination, or an LCD, by one or more of the regional Medicare Administrative Contractors ("MACs") who are private contractors that process and pay claims on behalf of CMS for different regions. In the absence of a specific NCD, as is the case with Zio XT historically and for Calendar Year 2021 following the Final Rule, the MAC with jurisdiction over a specific geographic region will have the discretion to make an LCD. The Company is seeking to establish LCD pricing with one or more MACs to establish pricing for 2021 and will be subject to LCD pricing until such time CMS establishes a NCD. On January 29, 2021, Novitas Solutions, the MAC which covers the region where the Company's IDTF in Houston, Texas is located and where almost all Medicare services for Zio XT are processed, published rates for 2021 that were significantly below our historical Medicare rates for Zio XT. The Company believes that the published rates by Novitas on January 29, 2021, are cross walked from CPT codes 93224 and 93226, which are existing CPT codes for external continuous electrocardiographic recording up to 48 hours, while the Zio service is capable of continuous monitoring for up to 14 days. The Company is the process of negotiating with Novitas to establish higher pricing for the Category I CPT Codes but can offer no assurances as to the timing or outcome of those discussions. If the published rates by Novitas remain unchanged or are not significantly improved for the CPT codes listed above thereby allowing us to obtain adequate Medicare reimbursement for the Zio service in the future, the Company may be unable to provide the Zio service or would experience a significant loss of revenue, either of which would have a material adverse effect on our cash flows, results of operations, and financial condition. The Company is currently holding a majority of Zio XT claims due to the CPT code transition. Claims are being held due to a combination of negotiations with payors and administrative delays with payors. The Company expects the level of held claims to remain high through the end of the first quarter of 2021 and potentially beyond. The high level of held claims will delay most first quarter 2021 cash flows into the second quarter of 2021 or potentially beyond, and may impact the timing and accounting for various income statement items, particularly revenue recognition and bad debt expense. The Company has adequate balance sheet liquidity to manage through these delays in cash flow timing. Further, a reduction in coverage by Medicare could cause some commercial third-party payors to implement similar reductions in their coverage or level of reimbursement of the Zio service. Given the evolving nature of the healthcare industry and on-going healthcare cost reforms, the Company will continue to be subject to changes in the level of Medicare coverage for its products, and unfavorable coverage determinations at the national or local level could adversely affect its results of operations. If published rates by Novitas are not increased to above the cost of revenue for the Zio service, and the Company is unable to achieve a level of revenues adequate to support its cost structure, this would raise substantial doubts about the Company's ability to continue as a going concern. Use of Estimates The preparation of the 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 as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, contractual allowances, allowance for doubtful accounts, the useful lives of property and equipment, the recoverability of long-lived assets including the estimated usage of the printed circuit board assemblies (“PCBAs”), the incremental borrowing rate for operating leases, accounting for income taxes, and various inputs used in estimating stock-based compensation. Certain of these estimates are impacted by uncertainties surrounding COVID-19 such as revenue recognition, contractual allowances for revenue, allowance for doubtful accounts, and stock based compensation. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that management believes are reasonable under the circumstances, including assumptions as to future events. Actual results may differ from those estimates. Fair Value of Financial Instruments The carrying amounts of certain of the Company’s financial instruments, which include cash equivalents, short-term investments, long-term investments, accounts receivable, accounts payable and accrued liabilities, approximate fair value due to their short maturities. Cash Equivalents Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less from the date of purchase. Investments Short-term investments consist of debt securities classified as available-for-sale and have maturities greater than 90 days, but less than one year as of the balance sheet date. Long-term investments have maturities greater than one year as of the balance sheet date. All investments are carried at fair value based upon quoted market prices. The Company periodically assesses its portfolio of debt investments for impairment. For debt securities in an unrealized loss position, this assessment first takes into account the intent to sell, or whether it is more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis. If either of these criteria are met, the debt security’s amortized cost basis is written down to fair value through interest and other, net. For debt securities in an unrealized loss position that do not meet the aforementioned criteria, the Company assesses whether the decline in fair value has resulted from credit losses or other factors. The Company evaluates expected credit losses by considering factors such as historical experience, market data, issuer-specific factors, and current economic conditions. Expected credit losses on available-for-sale debt securities are recognized in other income, net in the condensed consolidated statements of operations, and any remaining unrealized losses, net of taxes, are reported as a component of accumulated other comprehensive loss. The Company did not recognize any credit losses on its available-for-sale securities during the year ended December 31, 2020 and there were no impairment charges for unrealized losses in the periods presented. The cost of available-for-sale securities sold is based on the specific-identification method and realized gains and losses are included in earnings. Amortization of premiums and accretion of discounts are reported as a component of other income, net. Accounts Receivable, Allowance for Doubtful Accounts and Contractual Allowances Accounts receivable includes amounts due to the Company from healthcare institutions, third-party payors, and government payors and their related patients, as a result of the Company's normal business activities. Accounts receivable is reported on the consolidated balance sheets net of an estimated allowance for doubtful accounts and contractual allowances. The Company establishes an allowance for doubtful accounts for estimated uncollectible receivables based on its assessment of the collectability of customer accounts and recognizes the provision as a component of selling, general and administrative expenses. The Company records a provision for contractual allowances based on the estimated differences between contracted amounts and expected collection rates. Such provisions are based on the Company's historical experience and are reported as a reduction of revenue. The Company regularly reviews the allowances by considering factors such as historical experience, credit quality, the age of the accounts receivable balances, and current economic conditions that may affect a customer’s ability to pay. The following table presents the changes in the allowance for doubtful accounts (in thousands): Year ended December 31, 2020 2019 2018 Balance, beginning of year $ 9,049 $ 7,296 $ 4,486 Add: adoption of ASC 326 461 — — Add: provision for doubtful accounts 10,515 9,129 7,353 Less: write-offs, net of recoveries and other adjustments (7,314) (7,376) (4,543) Balance, end of year $ 12,711 $ 9,049 $ 7,296 The following table presents the changes in the contractual allowance (in thousands): Year ended December 31, 2020 2019 2018 Balance, beginning of year $ 15,433 $ 9,205 $ 6,345 Add: allowance for contractual adjustments 20,916 15,518 9,095 Less: contractual adjustments (15,068) (9,290) (6,235) Balance, end of year $ 21,281 $ 15,433 $ 9,205 Concentrations of Risk Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash and cash equivalents, investments and accounts receivable. Cash balances are deposited in financial institutions which, at times, may be in excess of federally insured limits. Cash equivalents are invested in highly rated money market funds. The Company invests in a variety of financial instruments, such as, but not limited to, United States Government securities, corporate notes, commercial paper and, by policy, limits the amount of credit exposure with any one financial institution or commercial issuer. The Company has not experienced any material losses on its deposits of cash and cash equivalents or investments. Concentrations of credit risk with respect to accounts receivable are limited due to the large number of customers comprising the Company’s customer base and their dispersion across many geographies. The Company does not require collateral. The Company records an allowance for doubtful accounts based on the assessment of the collectability of customer accounts, considering factors such as historical experience, credit quality, the age of the accounts receivable balances, and current economic conditions that may affect a customer’s ability to pay. Centers for Medicare and Medicaid Services (“CMS”), accounted for approximately 27%, 27% and 27% of the Company’s revenue for the years ended December 31, 2020, 2019 and 2018, respectively. CMS accounted for 20% and 20% of accounts receivable as of December 31, 2020 and 2019, respectively. Supply Risk The Company relies on single-source vendors to supply some of its disposable housings, instruments and other materials used to manufacture the Zio monitor and the adhesive that binds the Zio monitor to a patient’s body. These components and materials are critical, and there could be a considerable delay in finding alternative sources of supply. A global semiconductor supply shortage is having wide-ranging effects across multiple industries. The supply shortage has impacted multiple suppliers that provide the printed circuit board assemblies to the Company. The semiconductor supply shortage may have an impact on the Company until global supply is sufficient for global demand. Inventory Inventory owned by the Company is valued at cost, on the first in, first out (“FIFO”) basis, or the lower of cost or net realizable value. The Company records write-downs of inventory that is obsolete or in excess of anticipated demand. The Company also records market value based write-downs on consideration of product lifecycle stage, technology trends, product development plans and assumptions about future demand and market conditions. Actual demand may differ from forecasted demand, and such differences may have a material effect on recorded inventory values. Inventory write-downs are charged to cost of revenue and establish a new cost basis for the inventory. Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the assets, ranging from three Internal-Use Software The Company capitalizes costs related to internal-use software during the application development stage. Costs related to planning and post implementation activities are expensed as incurred. Capitalized internal-use software is amortized, and recognized as cost of revenue, on a straight-line basis over the estimated useful life, which is up to five years. The Company evaluates the useful lives of these assets on an annual basis, and tests for impairment whenever events or changes in circumstances occur that could impact the recoverability of these assets. Capitalized internal-use software costs are classified as a component of property and equipment. Goodwill Goodwill represents the excess of the purchase price paid over the fair value of tangible and identifiable intangible net assets acquired in business combinations. Goodwill is tested for impairment on an annual basis and at any other time if events occur or circumstances indicate that the carrying amount of goodwill may not be recoverable. Such events or circumstances may include significant adverse changes in the general business climate, among other things. The impairment test is performed by determining the enterprise fair value of the Company, which is primarily based on the Company’s market capitalization. If the Company’s carrying value, as a one reporting unit entity, is less than its fair value, then the fair value is allocated to all of its assets and liabilities (including any unrecognized intangible assets) as if the fair value was the purchase price to acquire the Company. The excess of the fair value over the amounts assigned to the Company’s assets and liabilities is the implied fair value of the goodwill. If the carrying amount of goodwill exceeds the implied fair value of that goodwill, an impairment loss is recognized in an amount equal to that excess. The Company performs its annual evaluation of goodwill during the fourth quarter of each fiscal year. The Company did not record any charges related to goodwill impairment in any of the periods presented in these consolidated financial statements. Impairment of Long-Lived Assets The Company annually reviews long-lived assets for impairment or whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparison of the carrying amount to the future net cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured as the amount by which the carrying amount of the assets exceeds the projected discounted future net cash flows arising from the asset. To date, there have been no such impairments of long-lived assets. Other Assets The Company uses Printed Circuit Board Assemblies (“PCBAs”), in each wearable Zio XT and Zio AT monitor as well as the wireless gateway used in conjunction with the ZIO AT monitor. The PCBAs are used numerous times and have useful lives beyond one year. Each time a PCBA is used in a wearable Zio XT or Zio AT monitor, or a wireless gateway is used with a Zio AT monitor a portion of the cost of the PCBA and/or gateway is recorded as a cost of revenue. The PCBAs are recorded as other assets and were $12.6 million and $7.4 million as of December 31, 2020 and 2019, respectively. The Company has based its estimates of how many times a PCBA can be used on testing in research and development, loss rates, product obsolescence, and the amount of time it takes the device to go through the manufacturing, shipping, customer shelf and patient wear time and upload process. The Company periodically evaluates the use estimate. Comprehensive Loss Comprehensive loss represents all changes in stockholders’ equity during the period from non-owner sources. The Company’s unrealized gains and losses on available-for-sale securities represent the only component of other comprehensive loss that are excluded from the reported net loss and that are presented in the consolidated statements of comprehensive loss. Revenue Recognition The Company’s revenue is generated primarily from the provision of its cardiac rhythm monitoring service, the Zio XT service. The Zio XT is a cardiac rhythm monitoring service that has a patient wear period of up to 14 days and is billable when the monitoring reports are delivered to the healthcare provider, which is also when the service is complete and the Company recognizes revenue. The time from when the patient has the Zio XT device applied to the time the report is posted is generally around 20 days. The Company has concluded that the Zio XT service is one performance obligation on the basis that the customer cannot benefit from each component of the service on its own or together with other resources that are readily available to the customer. The Zio AT mobile cardiac telemetry monitor, a wearable patch-based biosensor, offers what the Zio XT offers plus the additional capability of transmissions during the wear period to assist physicians in diagnosing and treating the small percentage of the population requiring more timely action. During the wear period, physicians will receive notifications if there are significant events that meet predetermined arrhythmia detection criteria. The Zio AT service revenue is recognized over the prescription period and delivery of an electronic Zio Report with two performance obligations. The Company recognizes as revenue the amount of consideration to which it expects to be entitled in exchange for performing the service. The consideration the Company is entitled to varies by portfolio, as further defined below, and includes estimates that require significant judgment by management. A unique aspect of healthcare is the involvement of multiple parties to the service transaction. In addition to the patient, often a third-party, for example a commercial or governmental payor or healthcare institution, will pay the Company for some or all of the service on the patient’s behalf. Separate contractual arrangements exist between the Company and third-party payors that establish amounts the third-party payor will pay on behalf of a patient for covered services rendered. A small portion of the Company’s transactions are covered by third-party payors with whom there is no contractual agreement or an established amount the third-party payor will pay. In determining the collectability and transaction price for its service, the Company considers factors such as insurance claims which are adjudicated as allowable under the applicable policy and payment history from both payors and patient out-of-pocket costs, payor coverage, whether there is a contract between the payor or healthcare institution and the Company, historical amount received for the service, and any current developments or changes that could impact reimbursement and healthcare institution payments. Certain of these factors are forms of variable consideration which are only included in the transaction price to the extent it is probable that a significant reversal of cumulative revenue will not occur when the uncertainty associated with the variable consideration is subsequently resolved. A summary of the payment arrangements with third-party payors and healthcare institutions is as follows: • Contracted third-party payors – The Company has contracts with negotiated prices for services provided for patients with commercial healthcare insurance carriers. • CMS – The Company has received independent diagnostic testing facility approval from regional Medicare Administrative Contractors and will receive reimbursement per the relevant Current Procedural Terminology (“CPT”) code rates for the services rendered to the patient covered by CMS. • Non-contracted third-party payors – Non-contracted commercial and government payors often reimburse out-of-network rates provided under the relevant CPT codes on a case-by-case basis. The transaction price used for determining revenue recognition is based on factors including an average of the Company’s historical collection experience for its non-contracted services. This rate is reviewed at least quarterly. • Healthcare institutions – Healthcare institutions are typically hospitals or physician practices in which the Company has negotiated amounts for its monitoring services, including certain governmental agencies such as the Veterans Administration and Department of Defense. The Company is utilizing the portfolio approach practical expedient under ASC 606 for revenue recognition whereby services provided under each of the above payor types form a separate portfolio. The Company accounts for the contracts within each portfolio as a collective group, rather than individual contracts. Based on history with these portfolios and the similar nature and characteristics of the patients within each portfolio, the Company has concluded that the financial statement effects are not materially different than if accounting for revenue on a contract-by-contract basis. For contracted and CMS portfolios, the Company recognizes revenue, net of contractual allowances, and recognizes an allowance for doubtful accounts for uncollectible patient accounts receivable. The transaction price is determined based on negotiated rates, and the Company has historical experience of collecting substantially all of these contracted rates. These contracts also impose a number of obligations regarding billing and other matters, and the Company’s noncompliance with a material term of such contracts may result in a denial of the claim. The Company accounts for denied claims as a form of variable consideration that is included as a reduction to the transaction price recognized as revenue. The Company estimates the denied claims which require management judgment. The estimated denied claims are based on historical information and judgement includes the historical period utilized. The Company monitors the estimated denied claims against the latest available information, and subsequent changes to the estimated denied claims are recorded as an adjustment to revenue in the periods during which such changes occur. Historical cash collection indicates that it is probable that substantially all of the transaction price, less the estimate of denied claims, will be received. Contracted payors may require that we bill patient co-payments and deductibles and from time to time we may not be able to collect such amounts due to credit risk. The Company provides for estimates of uncollectible patient accounts receivable, based upon historical experience where judgment includes the historical period utilized, at the time revenue is recognized, with such provisions presented as bad debt expense within the selling, general and administrative line item of the consolidated statement of operations. Adjustments to these estimates for actual experience are also recorded as an adjustment to bad debt expense. For non-contracted portfolios, the Company is providing an implicit price concession due to the lack of a contracted rate with the underlying payor, t |