Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less. Our cash equivalents consist of money market funds, which are not insured by the Federal Deposit Insurance Corporation (“FDIC”), that are primarily invested in short-term U.S. government obligations. Cash deposits at financial institutions may exceed the amount of insurance provided by the FDIC. Management believes that we are not exposed to significant credit risk on our cash deposits due to the financial position of the institutions in which deposits are held. We have not experienced any losses on our cash or cash equivalents.

We classify accounts receivable balances that are expected to be paid more than one year from the balance sheet date as non-current assets. The estimated timing of payment utilized as a basis for classification as non-current is determined by analyses of historical payor-specific payment experience, adjusted for known factors that are expected to change the timing of future payments.

We accrue an allowance for doubtful accounts against our accounts receivable when it is probable that an account is not collectible, based on write off history, credit risk of specific accounts, aging analysis and other information available on specific accounts. We generally do not perform evaluations of customers’ financial condition and generally do not require collateral. Accounts receivable are written off when all efforts to collect the balance have been exhausted. Historically, our bad debt expense has not been significant. The allowance for doubtful accounts was 0zero as of March 31,September 30, 2021, and December 31, 2020. Adjustments for implicit price concessions attributable to variable consideration, as discussed above, are incorporated into the measurement of the accounts receivable balances and are not part of the allowance for doubtful accounts.

We accrue for liabilities under discretionary employee and executive bonus plans. These estimated compensation liabilities are based on progress against corporate objectives approved by our board of directors, compensation levels of eligible individuals, and target bonus percentage levels. The board of directors reviews and evaluates the performance against these objectives and ultimately determines what discretionary payments are made. We also accrue for liabilities under employee sales incentive bonus plans with accruals based on performance achieved to date compared to established targets. As of March 31,September 30, 2021 and December 31, 2020, we accrued $2,664,000$8,999,000 and $7,175,000, respectively, for liabilities associated with these bonus plans. These amounts are classified as current or noncurrent accrued liabilities in the balance sheets based on the expected timing of payment.

Comprehensive (loss) incomeloss is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. Our comprehensive (loss) incomeloss was the same as our reported net (loss) incomeloss for all periods presented.

Once we satisfy our performance obligations and bill for the service, the timing of the collection of payments may vary based on the payment practices of the third-party payor and the existence of contractually established reimbursement rates. Most of the payments for our services are made by third-party payors, including Medicare and commercial health insurance carriers.

The Medicare claims that are covered by policy under a Local Coverage Determination (‘‘LCD’’) are generally paid at the established rate by our Medicare contractor within 30 days from receipt. Medicare claims that were either submitted to Medicare prior to the LCD coverage commencement date or are not covered by the terms of the LCD but meet the definition of being medically reasonable and necessary pursuant to the controlling Section 1862(a)(1)(A) of the Social Security Act are generally appealed and may ultimately be paid at the first (termed ‘‘redetermination’’), second (termed ‘‘reconsideration’’) or third level of appeal (de novo hearing with an Administrative Law Judge (“ALJ”)). A successful appeal at any of these levels results in payment.

In the absence of LCD coverage or contractually established reimbursements rates, we have concluded that our contracts include variable consideration because the amounts paid by Medicare or commercial health insurance carriers may be paid at

less than our standard rates or not paid at all, with such differences considered implicit price concessions. Variable consideration attributable to these price concessions is measured at the expected value using the ‘‘most likely amount’’ method under ASC 606. The amounts are determined by historical average collection rates by test type and payor category taking into consideration the range of possible outcomes, the predictive value of our past experiences, the time period of when uncertainties expect to be resolved and the amount of consideration that is susceptible to factors outside of our influence, such as the judgment and actions of third parties. Such variable consideration is included in the transaction price only to the extent it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainties with respect to the amount are resolved. Variable consideration may be constrained and excluded from the transaction price in situations where there is no contractually agreed upon reimbursement coverage or in the absence of a predictable pattern and history of collectability with a payor. Accordingly, in such situations revenues are recognized on the basis of actual cash collections. Variable consideration for Medicare claims that are not covered by an LCD, including those claims subject to approval by an ALJ at an appeal hearing, is deemed to be fully constrained due to factors outside our influence (i.e., judgment or actions of third parties) and the uncertainty of the amount to be received is not expected to be resolved for a long period of time. Variable consideration is evaluated each reporting period and adjustments are recorded as increases or decreases in revenues. Included in revenues for the three months ended March 31,September 30, 2021 and 2020 were $5,335,000$(92,000) and $3,160,000,$1,450,000, respectively, of net (negative) positive revenue increasesadjustments associated with changes in estimated variable consideration related to performance obligations satisfied in previous periods. Such amounts of variable consideration for the nine months ended September 30, 2021 and 2020 were $4,130,000 and $223,000, respectively. These amounts include (i) adjustments for actual collections versus estimated amounts and (ii) cash collections and the related recognition of revenue in current period for tests delivered in prior periods due to the release of the constraint on variable consideration.

Because our contracts with customers have an expected duration of one year or less, we have elected the practical expedient in ASC 606 to not disclose information about our remaining performance obligations. Any incremental costs to obtain contracts are recorded as selling, general and administrative expense as incurred due to the short duration of our contracts. Contract balances consisted of accounts receivable (both current and noncurrent) and the Medicare advance payment (discussed further below) as of March 31,September 30, 2021 and December 31, 2020.

On April 16, 2020, we received an advance payment of $8.3 million (the “Advance Payment”) from the Centers for Medicare & Medicaid Services (“CMS”) under its Accelerated and Advance Payment Program, which was expanded to provide increased cash flow to service providers during the COVID-19 pandemic. We have recordedRecoupment of the Advance Payment as a liability, consisting of both a current and noncurrent portion, on our balance sheet as of March 31, 2021. Recoupment will commencecommenced in April 2021 during which2021. For the first eleven months of recoupment, CMS will apply 25% of the Medicare payments otherwise owed to us against the balance of the Advance Payment. After thatthis eleven-month period, CMS will recoup at a rate of 50% of the Medicare payments otherwise owed to us for an additional six months. If the Advance Payment is not fully recovered by CMS after this recoupment period, we will be required to repay any remaining balance. As of March 31, 2021, no revenue has been recognized related to any portionThe remaining balance of the Advance Payment.

In June 2017, we submitted to the Office of Medicare Hearings and Appeals (‘‘OMHA’’) a formal request to participate in a program that OMHA developed with the intent of providing appellants a means to have large volumes of claim disputes adjudicated at an accelerated rate. The program consolidates outstanding claims at the ALJ level and uses a statistical-sampling approach where five ALJs will determine reimbursement results for a sample of claims which are then extrapolated to the universe of claims. The consolidation includes 2,698 DecisionDx-Melanoma claims dating from 2013 through spring 2017. Hearings were held in April 2019 with a supplemental hearing in May 2019. On March 12, 2020, OMHA issued a decision denying payment on all claims in the consolidation. We have filed an appeal to the decision, although no ruling on such appeal has been issued to date. In accordance with ASC 606 and consistent with prior periods, we have not recognized (fully constrained the variable consideration) any revenues attributable to these claims in our consolidated financial statements pending the outcome of this matter.

We rely upon reimbursements from third-party government payors (primarily Medicare) and private-payor insurance companies to collect accounts receivable related to sales of our diagnostic tests.

The table below provides the weighted-average number of potential common shares associated with outstanding securities not included in our calculation of diluted (loss)loss earnings per share for the three and nine months ended March 31,September 30, 2021 and 2020 because to do so would be antidilutive (in thousands):

Property and equipment, net consisted of the following (in thousands):

We use the Black-Scholes option pricing model to estimate the fair value of each option grant on the date of grant or any other measurement date. The following table sets forth the assumptions used to determine the fair value of stock options: