Summary of Significant Accounting Policies (Policies)	12 Months Ended
Dec. 31, 2015
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”). .
Need to Raise Additional Capital	Need to Raise Additional Capital The Company has incurred net losses since its inception and anticipates net losses and negative operating cash flows for the near future. For the year ended December 31, 2015, the Company had a net loss of $70.3 million, and as of December 31, 2015, it had an accumulated deficit of $250.1 million. At December 31, 2015, the Company had $28.9 million in cash and cash equivalents and $201.6 million in marketable securities. While the Company has introduced multiple products that are generating revenues, these revenues have not been sufficient to fund all operations. Accordingly, the Company has funded the portion of operating costs that exceeds revenues through a combination of equity issuances, debt issuances, and other financings. The Company expects to develop and commercialize future products and, consequently, it will need to generate additional revenues to achieve future profitability and may need to raise additional equity or debt financing that may not be available, if at all, at terms acceptable to the Company to fund future operations. Based on our current business plan, we believe that our existing cash and marketable securities will be sufficient to meet our anticipated cash requirements for the next 12 months.
Principles of Consolidation	Principles of Consolidation The accompanying condensed consolidated financial statements include all the accounts of the Company and its subsidiary. The Company established a subsidiary that operates in the state of Texas in December 2014 to support the Company’s laboratory and operational functions, which became active in the second quarter of 2015. All intercompany balances and transactions have been eliminated.
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions about future events that affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenues and expenses. Significant items subject to such estimates include the allowance for doubtful accounts, accrued liability for potential refund requests, stock-based compensation, the fair value of common stock and fair value of debt accounted for under ASC 815, as well as income tax uncertainties. These estimates and assumptions are based on management's best estimates and judgment. Management regularly evaluates its estimates and assumptions using historical experience and other factors; however, actual results could differ from these estimates and could have an adverse effect on the Company's financial statements.
Fair Value	Fair Value The Company discloses the fair value of financial instruments for financial assets and liabilities for which the value is practicable to estimate. Fair value is defined as the price that would be received upon the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). The Company carried senior secured term loan and warrants at fair value according to the fair value measurement guidance.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of cash and money market deposits with financial institutions.
Restricted Cash	Restricted Cash The Company discloses both short-term and long-term restricted cash. Short-term restricted cash consists of $0.8 million, securing our letter of credit for our headquarters operating lease which expires in October 2016 and $0.1 million in payments received by certain customers. Long-term restricted cash consists of $0.4 million deposit per credit card terms and $0.3 million securing our letter of credit for our headquarters operating lease which expires in January 2017.
Investments	Investments Management determines the appropriate classification of securities at the time of purchase and reevaluates such determination at each balance sheet date. The Company generally classifies its entire investment portfolio as available-for-sale. The Company views its available-for-sale portfolio as available for use in current operations. Accordingly, the Company classifies all investments as short-term, even though the stated maturity may be more than one year from the current balance sheet date. Available-for-sale securities are carried at fair value, with unrealized gains and losses reported in accumulated other comprehensive income (loss), which is a separate component of stockholders’ equity (deficit).
Risk and Uncertainties	Risk and Uncertainties Financial instruments that potentially subject the Company to credit risk consist of cash, accounts receivable and investments. The Company limits its exposure to credit loss by placing its cash in financial institutions with high credit ratings. The Company's cash may consist of deposits held with banks that may at times exceed federally insured limits. The Company performs evaluations of the relative credit standing of these financial institutions and limits the amount of credit exposure with any one institution. The Company bills third-party payers for certain tests performed. The amount that is ultimately received from the payer for our claim and the timing of such payments are subject to the determination of the payer based on the nature of the test performed and their view of our business practices with respect to collections of plan deductibles and co-payments from patients and other activities. This determination can impact both the amount and timing of when our invoices are collected. Payers may also withhold payments and request refunds of prior payments if we do not perform in accordance with the policies of these payers. The Company performs evaluations of financial conditions for clinics and laboratory partners and generally does not require collateral to support credit sales. For 2015 and 2014, there were no customers exceeding 10% in total revenue. For 2013, two customers accounted for more than 10% of our revenues: Quest Diagnostics Incorporated (16%) and Progenity, Inc. (12%). As of December 31, 2015 and 2014, no customers had a receivable balance greater than 10% of net accounts receivable, and as of December 31, 2013, two customers had receivable balances of 37% and 18% of total accounts receivable.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts Trade accounts receivable are recorded at the amount billed to the laboratory partners and clinics. Reducing this amount is an allowance for doubtful accounts for estimated losses resulting from the inability of its customers to make the contracted payments. Management analyzes accounts receivable and historical bad debt experience, customer creditworthiness, current economic trends, and changes in customer payment history when evaluating the adequacy of the allowance for doubtful accounts. Accounts receivable are written off against the allowance when there is substantive evidence that the account will not be paid.
Revenue Recognition	Revenue Recognition The Company generally bills an insurance carrier, a clinic or a patient for the test upon delivery of the test result. The Company also bills patients directly for out-of-pocket costs not covered by their insurance carriers representing co-pays and deductibles in accordance with their insurance carrier and health plans. The Company may not get reimbursed for tests completed if the tests are not covered under the insurance carrier’s reimbursement policies or the Company is not a qualified provider to the insurance carrier. For tests performed, where an agreed upon reimbursement rate or fixed fee and a predictable history or likelihood of collections exists, the Company recognizes revenues upon delivery of the test report to the prescribing physician based on the established billing rate less contractual and other adjustments, such as an allowance for doubtful accounts, to arrive at the amount that the Company expects to collect. In all other situations, as the Company does not have a sufficient history of collection and is not able to determine collectability, the Company recognizes revenues when cash is received. From time to time, we receive requests for refunds of payments previously made by insurance carriers. The Company has established an accrued liability for potential refund requests based on our experience. In cases where the Company sells its tests through its laboratory partners, the majority of the laboratory partners bill the patient, clinic, or insurance carrier for the performance of the Company's tests. For tests sold through a limited number of its laboratory partners, the Company bills directly to a patient, clinic or insurance carrier, or a combination of the insurance carrier and patient for the fees. The Company considers its services rendered when it delivers reports of its test results to the laboratory partner, clinic or patient. When the Company has contracted fixed rates for its services and collectability of its revenues is reasonably assured, it recognizes revenues upon delivery of test reports. The fixed fees identified in contracts with laboratory partners change only if a pricing amendment is agreed upon between both parties. For cases in which there is no fixed price established with a laboratory partner, the Company then recognizes revenues from partner distributed tests on a cash basis. Certain of the Company's arrangements include multiple deliverables. For revenue arrangements with multiple deliverables, the Company evaluates each deliverable to determine whether it qualifies as a separate unit of accounting. This determination is based on whether the deliverable has "stand-alone value" to the customer and whether a general right of return exists. The consideration that is fixed or determinable is then allocated to each separate unit of accounting based on the relative selling price of each deliverable. The consideration allocated to each unit of accounting is recognized as the related goods or services are delivered, limited to the consideration that is not contingent upon future deliverables. The Company uses judgment in identifying the deliverables in its arrangements, assessing whether each deliverable is a separate unit of accounting, and in determining the best estimate of selling price for certain deliverables. The Company also uses judgment in determining the period over which the deliverables are recognized in certain of its arrangements. Any amounts received that do not meet the criteria for revenue recognition are recorded as deferred revenue until such criteria are met. The Company receives royalty revenue through the licensing and the provisioning of services to support the use of the Company's proprietary technology with its customer. Royalty revenues are recognized when earned under the terms of the related agreements and are included in Other Revenues in the statements of operations. The Company recognizes revenue from the cloud-based distribution service offering. The Company grants customers licenses to use the Company’s proprietary intellectual properties and the cloud-based Natera software, and provides the other services to support the use of the Company's proprietary technology with its customers. Natera’s proprietary software is used in connection with the analysis of DNA sequence data in a manner yielding a result indicating the likely presence or absence of full or partial chromosomal abnormalities. The licensees do not have the right to possess Natera software, but rather are treated as software as a service. The revenues are recognized on an accrual basis (assuming all revenue recognition criteria are met) under the terms of the related agreements and are included in other revenues in the statements of operation.
Cost of Product Revenues	Cost of Product Revenues Cost of product revenues includes the cost of materials, direct labor of laboratory personnel, equipment and infrastructure expenses associated with processing blood and other samples, quality control analyses, and shipping charges to transport samples and specimens from ordering physicians, clinics or individuals. Infrastructure expenses include allocated facility and related occupancy costs. Costs associated with the performance of diagnostic services are recorded as tests are processed. Costs associated with grants received are reported in research and development expenses.
Research and Development	Research and Development The Company records research and development costs in the period incurred. Research and development costs consist of personnel costs, contract services, cost of materials utilized in performing tests, costs of clinical trials and allocated facilities and related overhead expenses.
Advertising Costs	Advertising Costs The Company expenses advertising costs as incurred. The Company incurred advertising costs of $1.1 million, $1.1 million and $0.4 million during 2015, 2014 and 2013, respectively.
Product Shipment Costs	Product Shipment Costs The Company expenses product shipment costs in cost of product revenues in the accompanying statements of operations. Shipping and handling costs for the years ended December 31, 2015, 2014 and 2013 were $7.0 million, $4.5 million and $2.0 million, respectively.
Income Taxes	Income Taxes Income taxes are recorded in accordance with Financial Accounting Standards Board ASC Topic 740, Income Taxes ("ASC 740"), which provides for deferred taxes using an asset and liability approach. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Tax benefits are recognized when it is more likely than not that a tax position will be sustained during an audit. Deferred tax assets are reduced by a valuation allowance if current evidence indicates that it is considered more likely than not that these benefits will not be realized.
Stock Based Compensation	Stock‑Based Compensation Stock‑based compensation related to stock options granted to the Company’s employees is measured at the grant date based on the fair value of the award. The fair value is recognized as expense over the requisite service period, which is generally the vesting period of the respective awards. No compensation cost is recognized on stock options for employees who do not render the requisite service and therefore forfeit their rights to the stock options. The Company uses the Black‑Scholes option‑pricing model to estimate the fair value of its stock options. The Company accounts for stock options issued to non-employees based on the estimated fair value of the awards using the Black-Scholes option-pricing model. The measurement of stock-based compensation is subject to periodic adjustments as the underlying equity instruments vest, and the resulting change in value, if any, is recognized in the Company's statements of operations during the period that the related services are rendered. The Black-Scholes option-pricing model requires the input of the Company's expected stock price volatility, the expected life of the awards, a risk-free interest rate, and expected dividends. Determining these assumptions requires significant judgment. The expected term was based on the simplified method and where the Company did not qualify to use the simplified method, the Company used the lattice model, and the volatility rate was based on that of publicly traded companies in the DNA sequencing, diagnostics, or personalized medicine industries. When selecting the public companies in these industries to be used in the volatility calculation, companies were selected with comparable characteristics to the Company, including enterprise value and financial leverage. Companies were also selected with historical share price volatility sufficient to meet the expected life of the Company's stock options. The historical volatility data was computed using the daily closing prices for the selected companies' shares during the equivalent period of the calculated expected term of the Company's stock options. The expected life of the non-employee option grants was based on their remaining contractual life at the measurement date. The risk-free interest rate assumption was based on U.S. Treasury instruments with maturities that were consistent with the option's expected life. The expected dividend assumption was based on the Company's history and expectation of dividend payouts.
Warrants	Warrants The Company accounts for warrants to purchase shares of its common stock as a liability at fair value on the balance sheet date because the Company may be obligated to redeem these warrants at some point in the future. The warrants are subject to remeasurement at each balance sheet date, with changes in fair value recognized as a gain or loss from the changes in fair value of the warrants in the statements of operations. The Company will continue to adjust the liability for changes in fair value until such time that the warrants are converted or expire.
Capitalized Software Held for Internal Use	Capitalized Software Held for Internal Use We capitalize costs of software held for internal use during the application development stage of a project and amortize those costs over their estimated useful lives of three years. The net book value of capitalized software held for internal use was $0.8 million and $0 as of December 31, 2015 and 2014, respectively. Amortized expense for amounts previously capitalized for the year ended December 31, 2015 was $0.2 million.
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Comprehensive loss and its components encompass all changes in equity other than those with stockholders, and include net loss, unrealized gains and losses on available-for-sale marketable securities. As of December 31, 2015 and 2014, accumulated other comprehensive loss consisted of $1.4 million and nil of unrealized losses on available-for-sale marketable securities. There were no reclassifications out of accumulated other comprehensive loss during years ended December 31, 2015 and 2014
Property and Equipment	Property and Equipment Property and equipment, including purchased and internally developed software, are stated at cost. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets, which are generally three years. Leasehold improvements are amortized using the straight-line method over the estimated useful lives of the assets or the remaining term of the lease, whichever is shorter. The Company periodically reviews the depreciable lives assigned to property and equipment placed in service and change the estimates of useful lives to reflect the results of such reviews. During April 2015, the Company increased the depreciable lives of certain sequencing and automation machinery equipment from three years to five years. The effect of this change in estimate for the year ended December 31, 2015 was a decrease in loss from operations and net loss of $1.7 million, respectively. The effect of this change in estimate was a decrease in net basic and diluted loss per share of $0.07 for the year ended December 31, 2015.
Inventory	Inventory Inventory is valued at the lower of the standard cost, which approximates actual cost, or market. Cost is determined using the first-in, first-out ("FIFO") method. Inventory consisted entirely of supplies, which are consumed when providing its test reports, and therefore does not maintain any finished goods inventory. The Company enters into inventory purchases and commitments so that it can meet future delivery schedules based on forecasted demand for its tests.
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board or FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed below, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption. In August 2014, FASB issued Accounting Standards Update No. 2014‑15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (ASU 2014‑15). ASU 2014‑15 requires management to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. In doing so, companies will have reduced diversity in the timing and content of footnote disclosures compared to footnote disclosures under today’s guidance. ASU 2014‑15 is effective for the Company in the first quarter of 2016 with early adoption permitted. The Company does not believe the impact of adopting ASU 2014‑15 on its financial statements will be significant. In May 2014, FASB issued Accounting Standards Update No. 2014‑09, Revenue from Contracts with Customers (ASU 2014‑09) to provide guidance on revenue recognition. ASU 2014‑09 requires a company to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under today’s guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. In August 2015, FASB issued ASU 2015-14, which defers the effective date of ASU 2014-09 for all entities by one year. ASU 2014-09 is effective for the Company in the first quarter of 2018. ASU 2014-09, as amended by ASU 2015-14, is effective for the Company in the fiscal year beginning after December 15, 2017, and interim periods within those years with early adoption permitted up to the first quarter of 2017. Upon adoption, ASU 2014‑09 can be applied retrospectively to all periods presented or only to the most current period presented with the cumulative effect of changes reflected in the opening balance of retained earnings in the most current period presented. The Company is currently evaluating the impact of adopting ASU 2014‑09 on its financial statements. In April 2015, FASB issued Accounting Standards Update No. 2015‑03, Interest—Imputation of Interest (Subtopic 835‑30): Simplifying the Presentation of Debt Issuance Costs (ASU 2015‑03). ASU 2015‑03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. ASU 2015‑03 is effective for the Company in the first quarter of 2016 with early adoption permitted. The Company does not believe the impact of adopting ASU 2015‑03 on its financial statements will be significant. In April 2015, FASB issued Accounting Standards Update No. 2015‑05, Intangibles—Goodwill and Other—Internal‑Use Software (Subtopic 350‑40): Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement (ASU 2015‑05). ASU 2015‑05 provides guidance to clarify the customer’s accounting for fees paid in a cloud computing arrangement. ASU 2015‑05 is effective for the Company in the first quarter of 2016 with early adoption permitted. The Company is currently evaluating the impact of adopting ASU 2015‑05 on its financial statements. In July 2015, FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory (ASU 2015-11). ASU 2015-11 simplifies the subsequent measurement of inventory by replacing today’s lower of cost or market test with a lower of cost and net realizable value test. ASU 2015-11 is effective for the Company in the fiscal year beginning after December 15, 2016, and interim periods within those fiscal years. The Company is currently evaluating the impact of adopting ASU 2015‑11 on its financial statements. In November 2015, FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes, which simplifies the presentation of deferred taxes by requiring that deferred tax assets and liabilities be presented as noncurrent on the balance sheet. ASU 2015-17 is effective for the Company in the fiscal year beginning after December 15, 2016, and interim periods within those fiscal years. The Company is currently evaluating the impact of adopting ASU 2015‑17 on its financial statements. In February 2016, the FASB issued ASU No. 2016-2, Leases. ASU 2016-2 is aimed at making leasing activities more transparent and comparable, and requires substantially all leases be recognized by lessees on their balance sheet as a right-of-use asset and corresponding lease liability, including leases currently accounted for as operating leases. ASU 2016-2 is effective for the Company in the fiscal year beginning after December 15, 2018, and interim periods within those fiscal years with early adoption permitted. The Company is currently evaluating the impact of adopting ASU 2016-2 on its financial statements.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2015

Summary of Significant Accounting Policies

The accompanying consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”). .

Need to Raise Additional Capital

The Company has incurred net losses since its inception and anticipates net losses and negative operating cash flows for the near future. For the year ended December 31, 2015, the Company had a net loss of $70.3 million, and as of December 31, 2015, it had an accumulated deficit of $250.1 million. At December 31, 2015, the Company had $28.9 million in cash and cash equivalents and $201.6 million in marketable securities. While the Company has introduced multiple products that are generating revenues, these revenues have not been sufficient to fund all operations. Accordingly, the Company has funded the portion of operating costs that exceeds revenues through a combination of equity issuances, debt issuances, and other financings. The Company expects to develop and commercialize future products and, consequently, it will need to generate additional revenues to achieve future profitability and may need to raise additional equity or debt financing that may not be available, if at all, at terms acceptable to the Company to fund future operations. Based on our current business plan, we believe that our existing cash and marketable securities will be sufficient to meet our anticipated cash requirements for the next 12 months.

Principles of Consolidation

The accompanying condensed consolidated financial statements include all the accounts of the Company and its subsidiary. The Company established a subsidiary that operates in the state of Texas in December 2014 to support the Company’s laboratory and operational functions, which became active in the second quarter of 2015. All intercompany balances and transactions have been eliminated.

Use of Estimates

The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions about future events that affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenues and expenses. Significant items subject to such estimates include the allowance for doubtful accounts, accrued liability for potential refund requests, stock-based compensation, the fair value of common stock and fair value of debt accounted for under ASC 815, as well as income tax uncertainties. These estimates and assumptions are based on management's best estimates and judgment. Management regularly evaluates its estimates and assumptions using historical experience and other factors; however, actual results could differ from these estimates and could have an adverse effect on the Company's financial statements.

Fair Value

The Company discloses the fair value of financial instruments for financial assets and liabilities for which the value is practicable to estimate. Fair value is defined as the price that would be received upon the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). The Company carried senior secured term loan and warrants at fair value according to the fair value measurement guidance.

Cash and Cash Equivalents

Cash and cash equivalents consist of cash and money market deposits with financial institutions.

Restricted Cash

The Company discloses both short-term and long-term restricted cash. Short-term restricted cash consists of $0.8 million, securing our letter of credit for our headquarters operating lease which expires in October 2016 and $0.1 million in payments received by certain customers. Long-term restricted cash consists of $0.4 million deposit per credit card terms and $0.3 million securing our letter of credit for our headquarters operating lease which expires in January 2017.

Investments

Management determines the appropriate classification of securities at the time of purchase and reevaluates such determination at each balance sheet date. The Company generally classifies its entire investment portfolio as available-for-sale. The Company views its available-for-sale portfolio as available for use in current operations. Accordingly, the Company classifies all investments as short-term, even though the stated maturity may be more than one year from the current balance sheet date. Available-for-sale securities are carried at fair value, with unrealized gains and losses reported in accumulated other comprehensive income (loss), which is a separate component of stockholders’ equity (deficit).

Risk and Uncertainties

Financial instruments that potentially subject the Company to credit risk consist of cash, accounts receivable and investments. The Company limits its exposure to credit loss by placing its cash in financial institutions with high credit ratings. The Company's cash may consist of deposits held with banks that may at times exceed federally insured limits. The Company performs evaluations of the relative credit standing of these financial institutions and limits the amount of credit exposure with any one institution.

The Company bills third-party payers for certain tests performed. The amount that is ultimately received from the payer for our claim and the timing of such payments are subject to the determination of the payer based on the nature of the test performed and their view of our business practices with respect to collections of plan deductibles and co-payments from patients and other activities. This determination can impact both the amount and timing of when our invoices are collected. Payers may also withhold payments and request refunds of prior payments if we do not perform in accordance with the policies of these payers.

The Company performs evaluations of financial conditions for clinics and laboratory partners and generally does not require collateral to support credit sales. For 2015 and 2014, there were no customers exceeding 10% in total revenue. For 2013, two customers accounted for more than 10% of our revenues: Quest Diagnostics Incorporated (16%) and Progenity, Inc. (12%). As of December 31, 2015 and 2014, no customers had a receivable balance greater than 10% of net accounts receivable, and as of December 31, 2013, two customers had receivable balances of 37% and 18% of total accounts receivable.

Allowance for Doubtful Accounts

Trade accounts receivable are recorded at the amount billed to the laboratory partners and clinics. Reducing this amount is an allowance for doubtful accounts for estimated losses resulting from the inability of its customers to make the contracted payments. Management analyzes accounts receivable and historical bad debt experience, customer creditworthiness, current economic trends, and changes in customer payment history when evaluating the adequacy of the allowance for doubtful accounts. Accounts receivable are written off against the allowance when there is substantive evidence that the account will not be paid.

Revenue Recognition

The Company generally bills an insurance carrier, a clinic or a patient for the test upon delivery of the test result. The Company also bills patients directly for out-of-pocket costs not covered by their insurance carriers representing co-pays and deductibles in accordance with their insurance carrier and health plans. The Company may not get reimbursed for tests completed if the tests are not covered under the insurance carrier’s reimbursement policies or the Company is not a qualified provider to the insurance carrier. For tests performed, where an agreed upon reimbursement rate or fixed fee and a predictable history or likelihood of collections exists, the Company recognizes revenues upon delivery of the test report to the prescribing physician based on the established billing rate less contractual and other adjustments, such as an allowance for doubtful accounts, to arrive at the amount that the Company expects to collect. In all other situations, as the Company does not have a sufficient history of collection and is not able to determine collectability, the Company recognizes revenues when cash is received. From time to time, we receive requests for refunds of payments previously made by insurance carriers. The Company has established an accrued liability for potential refund requests based on our experience.

In cases where the Company sells its tests through its laboratory partners, the majority of the laboratory partners bill the patient, clinic, or insurance carrier for the performance of the Company's tests.

For tests sold through a limited number of its laboratory partners, the Company bills directly to a patient, clinic or insurance carrier, or a combination of the insurance carrier and patient for the fees. The Company considers its services rendered when it delivers reports of its test results to the laboratory partner, clinic or patient. When the Company has contracted fixed rates for its services and collectability of its revenues is reasonably assured, it recognizes revenues upon delivery of test reports. The fixed fees identified in contracts with laboratory partners change only if a pricing amendment is agreed upon between both parties. For cases in which there is no fixed price established with a laboratory partner, the Company then recognizes revenues from partner distributed tests on a cash basis.

Certain of the Company's arrangements include multiple deliverables. For revenue arrangements with multiple deliverables, the Company evaluates each deliverable to determine whether it qualifies as a separate unit of accounting. This determination is based on whether the deliverable has "stand-alone value" to the customer and whether a general right of return exists. The consideration that is fixed or determinable is then allocated to each separate unit of accounting based on the relative selling price of each deliverable. The consideration allocated to each unit of accounting is recognized as the related goods or services are delivered, limited to the consideration that is not contingent upon future deliverables. The Company uses judgment in identifying the deliverables in its arrangements, assessing whether each deliverable is a separate unit of accounting, and in determining the best estimate of selling price for certain deliverables. The Company also uses judgment in determining the period over which the deliverables are recognized in certain of its arrangements. Any amounts received that do not meet the criteria for revenue recognition are recorded as deferred revenue until such criteria are met.

The Company receives royalty revenue through the licensing and the provisioning of services to support the use of the Company's proprietary technology with its customer. Royalty revenues are recognized when earned under the terms of the related agreements and are included in Other Revenues in the statements of operations.

The Company recognizes revenue from the cloud-based distribution service offering. The Company grants customers licenses to use the Company’s proprietary intellectual properties and the cloud-based Natera software, and provides the other services to support the use of the Company's proprietary technology with its customers. Natera’s proprietary software is used in connection with the analysis of DNA sequence data in a manner yielding a result indicating the likely presence or absence of full or partial chromosomal abnormalities. The licensees do not have the right to possess Natera software, but rather are treated as software as a service. The revenues are recognized on an accrual basis (assuming all revenue recognition criteria are met) under the terms of the related agreements and are included in other revenues in the statements of operation.

Cost of Product Revenues

Cost of product revenues includes the cost of materials, direct labor of laboratory personnel, equipment and infrastructure expenses associated with processing blood and other samples, quality control analyses, and shipping charges to transport samples and specimens from ordering physicians, clinics or individuals. Infrastructure expenses include allocated facility and related occupancy costs. Costs associated with the performance of diagnostic services are recorded as tests are processed. Costs associated with grants received are reported in research and development expenses.

Research and Development

The Company records research and development costs in the period incurred. Research and development costs consist of personnel costs, contract services, cost of materials utilized in performing tests, costs of clinical trials and allocated facilities and related overhead expenses.

Advertising Costs

The Company expenses advertising costs as incurred. The Company incurred advertising costs of $1.1 million, $1.1 million and $0.4 million during 2015, 2014 and 2013, respectively.

Product Shipment Costs

The Company expenses product shipment costs in cost of product revenues in the accompanying statements of operations. Shipping and handling costs for the years ended December 31, 2015, 2014 and 2013 were $7.0 million, $4.5 million and $2.0 million, respectively.

Income Taxes

Income taxes are recorded in accordance with Financial Accounting Standards Board ASC Topic 740, Income Taxes ("ASC 740"), which provides for deferred taxes using an asset and liability approach. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Tax benefits are recognized when it is more likely than not that a tax position will be sustained during an audit. Deferred tax assets are reduced by a valuation allowance if current evidence indicates that it is considered more likely than not that these benefits will not be realized.

Stock Based Compensation

Stock‑Based Compensation

Stock‑based compensation related to stock options granted to the Company’s employees is measured at the grant date based on the fair value of the award. The fair value is recognized as expense over the requisite service period, which is generally the vesting period of the respective awards. No compensation cost is recognized on stock options for employees who do not render the requisite service and therefore forfeit their rights to the stock options. The Company uses the Black‑Scholes option‑pricing model to estimate the fair value of its stock options.

The Company accounts for stock options issued to non-employees based on the estimated fair value of the awards using the Black-Scholes option-pricing model. The measurement of stock-based compensation is subject to periodic adjustments as the underlying equity instruments vest, and the resulting change in value, if any, is recognized in the Company's statements of operations during the period that the related services are rendered.

The Black-Scholes option-pricing model requires the input of the Company's expected stock price volatility, the expected life of the awards, a risk-free interest rate, and expected dividends. Determining these assumptions requires significant judgment. The expected term was based on the simplified method and where the Company did not qualify to use the simplified method, the Company used the lattice model, and the volatility rate was based on that of publicly traded companies in the DNA sequencing, diagnostics, or personalized medicine industries. When selecting the public companies in these industries to be used in the volatility calculation, companies were selected with comparable characteristics to the Company, including enterprise value and financial leverage. Companies were also selected with historical share price volatility sufficient to meet the expected life of the Company's stock options. The historical volatility data was computed using the daily closing prices for the selected companies' shares during the equivalent period of the calculated expected term of the Company's stock options. The expected life of the non-employee option grants was based on their remaining contractual life at the measurement date. The risk-free interest rate assumption was based on U.S. Treasury instruments with maturities that were consistent with the option's expected life. The expected dividend assumption was based on the Company's history and expectation of dividend payouts.

Warrants

The Company accounts for warrants to purchase shares of its common stock as a liability at fair value on the balance sheet date because the Company may be obligated to redeem these warrants at some point in the future. The warrants are subject to remeasurement at each balance sheet date, with changes in fair value recognized as a gain or loss from the changes in fair value of the warrants in the statements of operations. The Company will continue to adjust the liability for changes in fair value until such time that the warrants are converted or expire.

Capitalized Software Held for Internal Use

We capitalize costs of software held for internal use during the application development stage of a project and amortize those costs over their estimated useful lives of three years. The net book value of capitalized software held for internal use was $0.8 million and $0 as of December 31, 2015 and 2014, respectively. Amortized expense for amounts previously capitalized for the year ended December 31, 2015 was $0.2 million.

Accumulated Other Comprehensive Loss

Comprehensive loss and its components encompass all changes in equity other than those with stockholders, and include net loss, unrealized gains and losses on available-for-sale marketable securities. As of December 31, 2015 and 2014, accumulated other comprehensive loss consisted of $1.4 million and nil of unrealized losses on available-for-sale marketable securities. There were no reclassifications out of accumulated other comprehensive loss during years ended December 31, 2015 and 2014

Property and Equipment

Property and equipment, including purchased and internally developed software, are stated at cost. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets, which are generally three years. Leasehold improvements are amortized using the straight-line method over the estimated useful lives of the assets or the remaining term of the lease, whichever is shorter. The Company periodically reviews the depreciable lives assigned to property and equipment placed in service and change the estimates of useful lives to reflect the results of such reviews. During April 2015, the Company increased the depreciable lives of certain sequencing and automation machinery equipment from three years to five years. The effect of this change in estimate for the year ended December 31, 2015 was a decrease in loss from operations and net loss of $1.7 million, respectively. The effect of this change in estimate was a decrease in net basic and diluted loss per share of $0.07 for the year ended December 31, 2015.

Inventory

Inventory is valued at the lower of the standard cost, which approximates actual cost, or market. Cost is determined using the first-in, first-out ("FIFO") method. Inventory consisted entirely of supplies, which are consumed when providing its test reports, and therefore does not maintain any finished goods inventory. The Company enters into inventory purchases and commitments so that it can meet future delivery schedules based on forecasted demand for its tests.

Recent Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board or FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed below, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption.

In August 2014, FASB issued Accounting Standards Update No. 2014‑15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (ASU 2014‑15). ASU 2014‑15 requires management to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. In doing so, companies will have reduced diversity in the timing and content of footnote disclosures compared to footnote disclosures under today’s guidance. ASU 2014‑15 is effective for the Company in the first quarter of 2016 with early adoption permitted. The Company does not believe the impact of adopting ASU 2014‑15 on its financial statements will be significant.

In May 2014, FASB issued Accounting Standards Update No. 2014‑09, Revenue from Contracts with Customers (ASU 2014‑09) to provide guidance on revenue recognition. ASU 2014‑09 requires a company to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under today’s guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. In August 2015, FASB issued ASU 2015-14, which defers the effective date of ASU 2014-09 for all entities by one year. ASU 2014-09 is effective for the Company in the first quarter of 2018. ASU 2014-09, as amended by ASU 2015-14, is effective for the Company in the fiscal year beginning after December 15, 2017, and interim periods within those years with early adoption permitted up to the first quarter of 2017. Upon adoption, ASU 2014‑09 can be applied retrospectively to all periods presented or only to the most current period presented with the cumulative effect of changes reflected in the opening balance of retained earnings in the most current period presented. The Company is currently evaluating the impact of adopting ASU 2014‑09 on its financial statements.

In April 2015, FASB issued Accounting Standards Update No. 2015‑03, Interest—Imputation of Interest (Subtopic 835‑30): Simplifying the Presentation of Debt Issuance Costs (ASU 2015‑03). ASU 2015‑03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. ASU 2015‑03 is effective for the Company in the first quarter of 2016 with early adoption permitted. The Company does not believe the impact of adopting ASU 2015‑03 on its financial statements will be significant.

In April 2015, FASB issued Accounting Standards Update No. 2015‑05, Intangibles—Goodwill and Other—Internal‑Use Software (Subtopic 350‑40): Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement (ASU 2015‑05). ASU 2015‑05 provides guidance to clarify the customer’s accounting for fees paid in a cloud computing arrangement. ASU 2015‑05 is effective for the Company in the first quarter of 2016 with early adoption permitted. The Company is currently evaluating the impact of adopting ASU 2015‑05 on its financial statements.

In July 2015, FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory (ASU 2015-11). ASU 2015-11 simplifies the subsequent measurement of inventory by replacing today’s lower of cost or market test with a lower of cost and net realizable value test. ASU 2015-11 is effective for the Company in the fiscal year beginning after December 15, 2016, and interim periods within those fiscal years. The Company is currently evaluating the impact of adopting ASU 2015‑11 on its financial statements.

In November 2015, FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes, which simplifies the presentation of deferred taxes by requiring that deferred tax assets and liabilities be presented as noncurrent on the balance sheet. ASU 2015-17 is effective for the Company in the fiscal year beginning after December 15, 2016, and interim periods within those fiscal years. The Company is currently evaluating the impact of adopting ASU 2015‑17 on its financial statements.

In February 2016, the FASB issued ASU No. 2016-2, Leases. ASU 2016-2 is aimed at making leasing activities more transparent and comparable, and requires substantially all leases be recognized by lessees on their balance sheet as a right-of-use asset and corresponding lease liability, including leases currently accounted for as operating leases. ASU 2016-2 is effective for the Company in the fiscal year beginning after December 15, 2018, and interim periods within those fiscal years with early adoption permitted. The Company is currently evaluating the impact of adopting ASU 2016-2 on its financial statements.