The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make certain estimates, assumptions and judgments that can affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the consolidated financial statements, as well as the reported amounts of revenue and expenses during the reporting periods. Such management estimates include, but not limited to the revenue recognition, stock-based compensation, employee benefit and pension plans, inventory valuation, accrued warranty, operating liabilities, business combinations, fair value measurement of investments and accounting for income taxes. Other estimates, assumptions and judgments made by management include restructuring and other related costs, manufacturing partner and supplier liabilities, allowances for sales returns, allowances for doubtful accounts, pension benefit cost and obligations, useful life of acquired intangibles and recoverability of property, plant and equipment, impairment loss related to facility abandonment, fair value measurement of the debt component of the convertible senior notes, and loss contingencies. The Company bases its assumptions on historical experience and also on assumptions that it believes are reasonable. Actual results could differ materially from those estimates. Further, the Company expects uncertainties around its key accounting estimates to continue to evolve depending on the duration and degree of impact associated with the recent outbreak of a novel strain of the coronavirus

Many of the Company's product sales are sold in combination with installation and deployment services along with initial hardware and software support. The Company's product sales are also sold at times with spares management, on-site hardware replacement services, network operations management, software subscription services, extended hardware warranty and training. Initial software and hardware support services are generally delivered over a one-year period in connection with the initial purchase. Software warranty provides customers with maintenance releases during the warranty support period and hardware warranty provides replacement or repair of equipment that fails to perform in line with specifications. Software subscription services include software warranty and additionally provides customers with rights to receive unspecified software product upgrades released during the support period.

Spares management and on-site hardware replacement services include the replacement of defective units at customer sites in accordance with specified service level agreements. Network operations management includes the day-to-day operation of a customer's network. These services are generally delivered on an annual basis. The Company evaluates each promised good and service in a contract to determine whether it represents a distinct performance obligation or should be accounted for as a combined performance obligation.

Services revenue includes software subscription services, installation and deployment services, spares management, on-site hardware replacement services, network operations management, extended hardware warranty and training. Revenue from software subscription services, spares management, on-site hardware replacement services, network operations management and extended hardware warranty contracts is deferred and is recognized ratably over the contractual support period, which is generally one year, as services are provided over the course of the entire period. Revenue related to training and installation and deployment services is recognized upon completion of the services.

Contracts and customer purchase orders are generally used to determine the existence of an arrangement. In addition, shipping documents and customer acceptances, when applicable, are used to verify delivery and transfer of title. The Company typically satisfies its performance obligations upon shipment or delivery of product depending on the contractual terms. Payment terms to customers generally range from net 30 to 120 days from invoice, which are considered to be standard payment terms. The Company assesses its ability to collect from its customers based primarily on the creditworthiness and past payment history of the customer.

The Company sells software licenses that provide customers the ability to purchase incremental bandwidth capacity on an already-deployed piece of hardware. Infinera Instant Bandwidth-enabled systems generally include a specific initial capacity and incremental capacity can be added by the purchase of Instant Bandwidth licenses. Instant Bandwidth licenses are considered distinct performance obligations because customers can provision additional transmission capacity on demand without the deployment of any incremental equipment.

Some contracts commit the customer to purchase incremental Instant Bandwidth licenses within a specified time frame from the initial shipment of the Instant Bandwidth-enabled hardware. The time frame varies by customer and generally ranges between 12 to 24 months. If the customer does not purchase the additional capacity within the time frame as stated in the contract, the Company has the right to deliver and invoice such Instant Bandwidth licenses to the customer. Future committed licenses are considered to be additional performance obligations when a minimum purchase obligation is present, as evidenced by enforceable rights and obligations. As such, the Company is required to estimate the variable consideration for future Instant Bandwidth licenses as part of determining the contract transaction price.

The contract term is determined on the basis of the period over which the parties to the contract have present enforceable rights and obligations. Certain customer contracts include a termination for convenience clause that allows the customer to terminate services without penalty, upon advance notification. For such contracts, the service duration is limited to the non-cancelable portion of the contract.

Stand-alone selling price is the price at which an entity would sell a good or service on a stand-alone (or separate) basis at contract inception. Under this model, the observable price of a good or service sold separately provides the best evidence of stand-alone selling price. However, in certain situations, stand-alone selling prices will not be readily observable and the entity must estimate the stand-alone selling price.

The majority of products and services offered by the Company have readily observable selling prices. For products and services that do not, the Company generally estimates stand-alone selling price using the market assessment approach based on expected selling price and adjust those prices as necessary to reflect the Company’s costs and margins. As part of its stand-alone selling price policy, the Company reviews product pricing on a periodic basis to identify any significant changes and revise its expected stand-alone selling price assumptions as appropriate.

The Company has assessed the treatment of costs to obtain or fulfill a contract with a customer. Sales commissions have historically been expensed as incurred. Under Topic 606, the Company capitalizes sales commissions related to multi-year service contracts, which are paid for upfront, and amortizes the asset over the period of benefit, which is the service period. Sales commissions paid on service contract renewals, are commensurate with the sales commissions paid on the initial contracts.

The Company’s remaining performance obligations represent the transaction price allocated to performance obligations that are unsatisfied or partially satisfied as of period end, consisting of deferred revenue and backlog. The Company’s backlog represents purchase orders received from customers for future product shipments and services that are unsatisfied or partially satisfied as of period end. The Company’s backlog is subject to future events that could cause the amount or timing of the related revenue to change, and, in certain cases, may be canceled without penalty. Orders in backlog may be fulfilled several quarters following receipt or may relate to multi-year support service obligations.

The Company granted performance shares (“PSUs”) to its executive officers and senior management in 2017 and 2018. The PSUs granted during 2017 and 2018 to the Company’s executive officers and senior management are based on the TSR of the Company’s common stock price relative to the TSR of the individual companies listed in the S&P North American Technology Multimedia Networking Index (SPGIIPTR) (the “S&P Networking Index”) over the span of one year, two years and three years. The number of shares to be issued upon vesting of these PSUs range from zero to two times the target number of PSUs granted depending on the Company’s performance against the individual companies listed in the S&P Networking Index. This performance metric is classified as a market condition.

PSUs granted to the Company's executive officers and senior management during 2019 and 2020 are based on performance criteria related to a specific financial target over the span of a three-year performance period. These PSUs may become eligible for vesting to begin before the end of the three year performance period, if the applicable financial target is met. The number of shares to be issued upon vesting of these PSUs is capped at the target number of PSUs granted. The Company assesses the achievement status of these PSUs on a quarterly basis and records the related stock-based compensation expenses based on the estimated achievement payout.

The Company uses a Monte Carlo simulation model to determine the fair value of PSUs with market conditions. The Monte Carlo simulation model is based on a discounted cash flow approach, with the simulation of a large number of possible stock price outcomes for the Company's stock and the target composite index. The use of the Monte Carlo simulation model requires the input of a number of assumptions including expected volatility of the Company's stock price, expected volatility of a target composite index, correlation between changes in the Company's stock price and changes in the target composite index, risk-free interest rate, and expected dividends as applicable. Expected volatility of the Company's stock is based on the weighted-average historical volatility of its stock. Expected volatility of the target composite index is based on the historical and implied data. Correlation is based on the historical relationship between the Company's stock price and the target composite index average. The risk-free interest rate is based upon the treasury zero-coupon yield appropriate for the term of the PSU as of the grant date. The expected dividend yield is zero for the Company as it does not expect to pay dividends in the future. The expected dividend yield for the target composite index is the annual dividend yield expressed as a percentage of the composite average of the target composite index on the grant date.

The Company operates a number of post-employment plans in Germany, as well as smaller post-employment plans in other countries, including both defined contribution and defined benefit plans. Benefit cost and obligations pertaining to these plans are based on assumptions for the discount rate, expected return on plan assets, mortality rates, expected salary increases, health care cost trend rates and attrition rates. The discount rate assumption is based on current investment yields of high-quality fixed-income securities with maturities similar to the expected benefits payment period. Mortality rates help predict the expected life of plan participants. The expected increase in the compensation levels assumption reflects the Company's actual experience and future expectations. The expected long-term return on plan assets is determined based on asset allocations, historical portfolio results, historical asset correlations and management’s expected returns for each asset class. The Company evaluates its expected return assumptions annually including reviewing current capital market assumptions to assess the reasonableness of the expected long-term return on plan assets. The Company updates the expected long-term return on assets when the Company observes a sufficient level of evidence that would suggest the long-term expected return has changed.

All costs to develop the Company’s hardware products are expensed as incurred. Software development costs are capitalized beginning when a product’s technological feasibility has been established and ending when a product is available for general release to customers. Generally, the Company’s software products are released soon after technological feasibility has been established. As a result, costs subsequent to achieving technological feasibility have not been significant and all software development costs have been expensed as incurred.

As part of the process of preparing the Company's consolidated financial statements, the Company is required to estimate its taxes in each of the jurisdictions in which it operates. The Company estimates actual current tax expense together with assessing temporary differences resulting from different treatment of items, such as accruals and allowances not currently deductible for tax purposes. These differences result in deferred tax assets and liabilities, which are included in its consolidated balance sheets. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in its consolidated statements of operations become deductible expenses under applicable income tax laws or loss, or credit carryforwards are utilized. Accordingly, realization of the Company's deferred tax assets is dependent on future taxable income within the respective jurisdictions against which these deductions, losses and credits can be utilized within the applicable future periods.

The Company must assess the likelihood that some portion or all of its deferred tax assets will be recovered from future taxable income within the respective jurisdictions, and to the extent the Company believes that recovery does not meet the “more-likely-than-not” standard, it must establish a valuation allowance. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management judgment is required in determining the Company’s provision for income taxes, the Company’s deferred tax assets and liabilities, and any valuation allowance recorded against the Company’s net deferred tax assets. In evaluating the need for a full or partial valuation allowance, all positive and negative evidence must be considered, including the Company's forecast of taxable income over the applicable carryforward periods, its current financial performance, its market environment, and other factors. Based on the available objective evidence, at December 26, 2020, the Company believes it is not more likely than not that the domestic net deferred tax assets will be realizable in the foreseeable future. Accordingly, the domestic net deferred tax assets are subject to a full valuation allowance. To the extent that the Company determines that deferred tax assets are realizable on a more likely than not basis, and an adjustment is needed, that adjustment will be recorded in the period that the determination is made.

date, revenue, costs and expenses are translated at average exchange rates in effect during the period. Equity transactions are translated using historical exchange rates. The effects of foreign currency translation adjustments are recorded as a separate component of accumulated other comprehensive income (loss) in the accompanying consolidated balance sheets.

For all non-functional currency account balances, the re-measurement of such balances to the functional currency will result in either a foreign exchange transaction gain or loss, which is recorded to other gain (loss), net, in the same period that the re-measurement occurred. Aggregate foreign exchange transactions recorded in 2020, 2019 and 2018 were losses of $0.2 million, $3.7 million, and $2.5 million, respectively.

The Company also enters into foreign currency exchange contracts to reduce the volatility of cash flows primarily related to forecasted revenues and expenses denominated primarily in euros and British pounds. The gains and losses on these foreign currency derivatives are recorded to the consolidated statement of operations line item, in the current period, to which the item that is being economically hedged is recorded.

The Company considers all highly liquid investments with an original maturity at the date of purchase of 90 days or less to be cash equivalents and those with a maturity between 90 days and one year to be short-term investments. The Company classifies debt instruments with remaining maturities greater than one year as long-term investments, unless the Company intends to settle its holdings within one year or less and in such case it is considered to be short-term investments. The Company determines the appropriate classification of its marketable securities at the time of purchase and re-evaluates such designations as of each balance sheet date.

Available-for-sale investments are stated at fair market value with unrealized gains and losses recorded in accumulated other comprehensive income (loss) in the Company’s consolidated balance sheets. The Company evaluates its available-for-sale marketable debt securities for other-than-temporary impairments and records any credit loss portion in other income (expense), net, in the Company’s consolidated statements of operations. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity and for any credit losses incurred on these securities. Gains and losses are recognized when realized in the Company’s consolidated statements of operations under the specific identification method.

Pursuant to the accounting guidance for fair value measurements and its subsequent updates, fair value is defined as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities required or permitted to be recorded at fair value, the Company considers the principal or most advantageous market in which it would transact and it considers assumptions that market participants would use when pricing the asset or liability.

Valuation techniques used by the Company are based upon observable and unobservable inputs. Observable or market inputs reflect market data obtained from independent sources, while unobservable inputs reflect the Company’s assumptions about market participant assumptions based on the best information available. Observable inputs are the preferred source of values. These two types of inputs create the following fair value hierarchy:

Level 1

–

Quoted prices in active markets for identical assets or liabilities.

Level 2

–

Quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3

–

Prices or valuations that require management inputs that are both significant to the fair value measurement and unobservable.

As discussed in Note 6, “Derivative Instruments" to the Notes to Consolidated Financial Statements, the Company mainly holds non-speculative foreign exchange forward contracts to hedge certain foreign currency exchange exposures. The Company estimates the fair values of derivatives based on quoted market prices or pricing models using current market rates. Where applicable, these models project future cash flows and discount the future amounts to a present value using market-based observable inputs including interest rate curves, credit risk, foreign exchange rates, and forward and spot prices for currencies.

As a result of the Acquisition, the Company acquired a number of post-employment plans in Germany, as well as a number of smaller post-employment plans in other countries, including both defined contribution and defined benefit plans. The defined benefit plans expose the Company to actuarial risks such as investment risk, interest rate risk, life expectancy risk and salary risk. The characteristics of the defined benefit plans and the risks associated with them vary depending on legal, fiscal, and economic requirements.

Accounts receivable are recorded at the invoiced amount and do not bear interest. The Company maintains an allowance for doubtful accounts for estimated credit losses resulting from the inability of its customers to make required payments and reviewed the allowance quarterly. The Company determines expected credit losses by performing credit evaluations of its customers' financial condition, establishing both a general reserve and specific reserve for customers in adverse financial condition and adjusting for its expectations of changes in conditions that may impact the collectability of outstanding receivables. The Company considers a customer's receivable balance past due when the amount is due beyond the credit terms extended, The Company considers factors such as historical experience, credit quality, age of the accounts receivable balances, and geographic or country-specific risks. Amounts are written off when receivables are determined to be uncollectible.

Customer product returns are approved on a case by case basis. Specific reserve provisions are made based upon a specific review of all the approved product returns where the customer has yet to return the products to generate the related sales return credit at the end of a period. Estimated sales returns are provided for as a reduction to revenue. At December 26, 2020, December 28, 2019 and December 29, 2018, revenue was reduced for estimated sales returns by $2.4 million, $3.5 million, and $4.3 million, respectively.

The risk with respect to accounts receivable is mitigated by ongoing credit evaluations that the Company performs on its customers. As the Company continues to expand its sales internationally, it may experience increased levels of customer credit risk associated with those regions. Collateral is generally not required for accounts receivable but may be used in the future to mitigate credit risk associated with customers located in certain geographical regions.

To date, a few of the Company’s customers have accounted for a significant portion of its revenue. One customer accounted for approximately 11%, 13% and 13% of the Company's revenue in each of 2020, 2019 and 2018, respectively. One other customer accounted for approximately 15% of the Company's revenue in 2018. No other customers accounted for over 10% of the Company's revenue in 2020, 2019 or 2018.

The Company depends on sole source or limited source suppliers for several key components and raw materials. The Company generally purchases these sole source or limited source components and raw materials through standard purchase orders and does not have long-term contracts with many of these limited-source suppliers. While the Company seeks to maintain sufficient reserve stock of such components and raw materials, the Company’s business and results of operations could be adversely affected if any of its sole source or limited source suppliers suffer from capacity constraints, lower than expected yields, deployment delays, work stoppages or any other reduction or disruption in output.

The Company is exposed to foreign currency exchange rate fluctuations in the normal course of its business. As part of its risk management strategy, the Company uses derivative instruments, specifically forward contracts, to reduce the impact of foreign exchange fluctuations on earnings. The forward contracts are with high-quality institutions and the Company monitors the creditworthiness of the counterparties consistently. The Company’s objective is to offset gains and losses resulting from these exposures with gains and losses on the derivative contracts used to hedge them, thereby reducing volatility of earnings or protecting fair values of assets. The Company does not use derivative contracts for trading or speculative purposes.

The Company enters into foreign currency exchange forward contracts to manage its exposure to fluctuations in foreign exchange rates that arise primarily from euro and British pounds. Gains and losses on these contracts are intended to offset the impact of foreign exchange rate changes on the underlying, and therefore, do not subject the Company to material balance sheet risk. The Company also enters into foreign currency exchange contracts to reduce the volatility of cash flows primarily related to forecasted revenues and expenses denominated in euros and British pounds. These contracts are generally settled for U.S. dollars, euros and British pounds at maturity.

The Company has entered into factoring agreements, to sell certain receivables to unrelated third-party financial institutions. These transactions are accounted for in accordance with ASC Topic 860, “Transfers and Servicing” (“ASC 860”). ASC 860 and result in a reduction in accounts receivable because the agreements transfer effective control over and risk related to the receivables to the buyers. The Company's factoring agreements do not allow for recourse in the event of uncollectability, and the Company does not retain any interest in the underlying accounts receivable once sold.

Inventories consist of raw materials, work-in-process and finished goods and are stated at standard cost adjusted to approximate the lower of actual cost or net realizable value. Costs are recognized utilizing the first-in, first-out method. Net realizable value is based upon an estimated selling price reduced by the estimated cost of disposal. The determination of market value involves numerous judgments including estimated average selling prices based upon recent sales volumes, industry trends, existing customer orders, current contract price, future demand and pricing and technological obsolescence of the Company’s products.

valuing its inventory costs and deferred inventory costs, the Company considered whether the net realizable value of inventory delivered or expected to be delivered at less than cost, primarily comprised of common equipment, had declined. The Company concluded that, in the instances where the net realizable value of inventory delivered or expected to be delivered was less than cost, it was appropriate to value the inventory costs and deferred inventory costs at cost or net realizable value, whichever is lower, thereby recognizing the cost of the reduction in net realizable value of inventory in the period in which the reduction occurred or can be reasonably estimated. The Company has, therefore, recognized inventory write-downs as necessary in each period in order to reflect inventory at the lower of actual cost or net realizable value.

The Company considers whether it should accrue losses on firm purchase commitments related to inventory items. Given that the net realizable value of common equipment is below contractual purchase price, the Company has also recorded losses on these firm purchase commitments in the period in which the commitment is made. When the inventory parts related to these firm purchase commitments are received, that inventory is recorded at the purchase price less the accrual for the loss on the purchase commitment.

Property, plant and equipment are stated at cost. This includes enterprise-level business software that the Company customizes to meet its specific operational needs and certain software licenses. Depreciation is calculated using the straight-line method over the estimated useful lives of the respective assets. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or estimated useful life of the asset. An assumption of lease renewal where a renewal option exists is used only when the renewal has been determined to be reasonably certain. Repair and maintenance costs are expensed as incurred. The estimated useful life for each asset category is as follows:

The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of these assets may not be recoverable or that the useful life is shorter than originally estimated. If impairment indicators are present and the projected future undiscounted cash flows are less than the carrying value of the assets, the carrying values are reduced to the estimated fair value. If assets are determined to be recoverable, but the useful lives are shorter than originally estimated, the carrying value of the assets is depreciated over the newly determined remaining useful lives.

In the Company's contracts with its customers, the Company warrants that its products will operate substantially in conformity with product specifications. Hardware warranties provide the purchaser with protection in the event that the product does not perform to product specifications. During the warranty period, the purchaser’s sole and exclusive remedy in the event of such defect or failure to perform is limited to the correction of the defect or failure by repair, refurbishment or replacement, at the Company’s sole option and expense. The Company's hardware warranty periods generally range from one to five years from date of acceptance for hardware and the Company's software warranty is 90 days. Upon delivery of the Company's products, the Company provides for the estimated cost to repair or replace products that may be returned under warranty. The hardware warranty accrual is based on actual historical returns and cost of repair experience and the application of those historical rates to the Company's in-warranty installed base. The provision for warranty claims fluctuates depending upon the installed base of products and the failure rates and costs of repair associated with these products under warranty. Furthermore, the Company's costs of repair vary based on repair volume and its ability to repair, rather than replace, defective units. In the event that actual product failure rates and costs to repair differ from the Company's estimates, revisions to the warranty provision are required. In addition, from time to time, specific hardware warranty accruals may be made if unforeseen technical problems arise with specific products. The Company regularly assesses the adequacy of its recorded warranty liabilities and adjusts the amounts as necessary.

Accounting for acquisitions requires the Company's management to estimate the fair value of the assets and liabilities assumed, which requires management to make significant estimates, judgments, and assumptions that could materially affect the timing or amounts recognized in its financial statements. These assumptions and estimates include the Company’s use of the asset and the appropriate discount rates. The Company’s significant estimates can include, but are not limited to, the future cash flows, the appropriate weighted cost of capital, and discount rates, as well as the estimated useful life of intangible assets, deferred tax assets and liabilities, uncertain tax positions, and tax-related valuation allowance, which are initially estimated as of the acquisition date. While the Company uses its best estimates and assumptions to accurately value assets acquired and liabilities assumed at the acquisition date, the estimates are inherently uncertain and subject to refinement. In addition, unanticipated events and circumstances may occur that may affect the accuracy or validity of such estimates. As a result, during the measurement period, which may be up to one year following the acquisition date, if new information is obtained about facts and circumstances that existed as of the acquisition date, the Company may record adjustments to the fair value of these assets and liabilities, with the corresponding offset to goodwill.

Intangible assets with finite lives are carried at cost, less accumulated amortization. Amortization is computed over the estimated useful lives of the respective assets. In-process research and development represent the fair value of incomplete research and development projects that have not reached technological feasibility as of the date of acquisition. Initially, these assets are not subject to amortization, but once projects have been completed, these assets are transferred to developed technology, which are subject to amortization, while assets related to projects that have been abandoned are impaired and expensed to research and development.

Goodwill represents the excess of the purchase price of an acquired business over the fair value of the identifiable assets acquired and liabilities assumed. The Company tests for impairment of goodwill on an annual basis in the fourth quarter and at any other time when events occur or circumstances indicate that the carrying amount of goodwill may not be recoverable. The Company has the option to first assess qualitative factors to determine whether it is necessary to perform the quantitative goodwill impairment test. If the Company determines that as a result of the qualitative assessment that it is more likely than not (i.e., greater than 50% likelihood) that the fair value of a reporting unit is less than its carrying amount, then the quantitative test is required or it can directly perform the quantitative analysis. The Company recognizes an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized does not exceed the total amount of goodwill allocated to that reporting unit.

The Company evaluates events and changes in circumstances that could indicate carrying amounts of purchased intangible assets may not be recoverable. When such events or changes in circumstances occur, the Company assesses the recoverability of these assets by determining whether or not the carrying amount will be recovered through undiscounted expected future cash flows. If the total of the future undiscounted cash flows is less than the carrying amount of an asset, the Company records an impairment loss for the amount by which the carrying amount of the asset exceeds the fair value of the asset.

Effective December 30, 2018, the Company adopted Accounting Standards Update No. 2016-02, “Leases (Topic 842)” (“Topic 842”) utilizing the modified retrospective transition method, which requires a cumulative-effect adjustment, if any, to the opening balance of retained earnings to be recognized on the date of adoption with prior periods not restated.

The Company determines if an arrangement contains a lease at inception. Operating leases are included in operating lease right of use ("ROU") assets, accrued expenses and operating lease liabilities on the Company's consolidated balance sheets. Finance leases are included in property, plant and equipment, accrued expenses and finance lease liabilities on the Company's consolidated balance sheets.

Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. As most of the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. Operating lease ROU assets also include any lease payments made and exclude lease incentives and initial direct costs incurred. Variable lease payments are expensed as incurred and are not included within the ROU asset and lease liability calculation. Variable lease payments primarily include reimbursements of costs incurred by lessors for common area maintenance and utilities. The Company's lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. The Company rents or subleases certain real estate under agreements that are classified as operating leases.

Upon abandoning or committing to a plan to abandon a leased property in the short term before the lease term expires, the Company assesses the fair value of its remaining obligation under the lease and records an impairment of the ROU asset, if needed. The impairment loss is calculated as the present value of the amount by which the remaining lease obligation, adjusted for the effects of any one-time costs to sublease, exceeds the estimated sublease rentals that could be reasonably obtained. The estimated sublease rentals consider Company's ability and intent to sublease the space. The significant assumptions used in the Company's discounted cash flow model include the amount and timing of estimated sublease rental receipts and the discount rate which involve a number of risks and uncertainties, some of which are beyond control, including future real estate market conditions and the Company's ability to successfully enter into subleases or termination agreements with terms as favorable as those assumed when arriving at its estimates. The Company monitors these estimates and assumptions on at least a quarterly basis for changes in circumstances and any corresponding adjustments to the accrual are recorded in its statement of operations in the period when such changes are known.

The Company records costs associated with exit activities related to restructuring plans in accordance with ASC 420, “Exit or Disposal Cost Obligations.” Liabilities for costs associated with an exit or disposal activity are recognized in the period in which the liability is incurred. The timing of the associated cash payments is dependent upon the type of exit cost and extends over an approximately four-year period. The Company records restructuring cost liabilities in “Accrued Expenses” and "Other Long-term Liabilities" in the Consolidated Balance Sheet.

Restructuring costs include employee and contract termination costs, facility consolidation and closure costs, equipment write-downs and inventory write-downs. One-time termination benefits are recognized as a liability at estimated fair value when the approved plan of termination has been communicated to employees, unless employees must provide future service, in which case the benefits are recognized ratably over the future service period. Ongoing termination benefits arrangements are recognized as a liability at estimated fair value when the amount of such benefits becomes estimable and payment is probable.

Restructuring charges require significant estimates and assumptions, including estimates made for employee separation costs and other contract termination charges. Management estimates involve a number of risks and uncertainties, some of which are beyond control, including the Company's ability to successfully enter into termination agreements with employees and others with terms as favorable as those assumed when arriving at its estimates. The Company monitors these estimates and assumptions on at least a quarterly basis for changes in circumstances and any corresponding adjustments to the accrual are recorded in its statement of operations in the period when such changes are known.

In June 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-13, "Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments", in order to improve financial reporting of expected credit losses on financial instruments and other commitments to extend credit. Topic 326 requires that an entity measure and recognize expected credit losses for financial assets held at amortized cost and replaces the incurred loss impairment methodology in prior U.S. GAAP with a methodology that requires consideration of a broader range of information to estimate credit losses. The Company adopted Topic 326 on a modified retrospective basis in the first quarter of 2020 through a cumulative-effect adjustment at the beginning of the first quarter of 2020 and the impact of the adoption was not material to the Company's consolidated financial statements as credit losses are not expected to be significant based on historical collection trends, the financial condition of the Company’s customers, and external market factors. The Company will continue to actively monitor the impact of the COVID-19 pandemic on expected credit losses.

In August 2018, the FASB issued ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement” (“ASU 2018-13”). This update eliminates, adds and modifies certain disclosure requirements for fair value measurements. ASU 2018-13 was effective for the Company in its first quarter of 2020. The Company adopted ASU 2018-13 in the first quarter of 2020 and the impact of the adoption was not material to the Company's consolidated financial statements.

In August 2018, the FASB issued ASU 2018-14, “Compensation - Retirement Benefits - Defined Benefit Plans - General (Subtopic 715-20): Disclosure Framework - Changes to the Disclosure Requirements for Defined Benefit Plans” (“ASU 2018-14”). This update eliminates, adds and modifies certain disclosure requirements for employers that sponsor defined benefit pension or other post-retirement plans. The ASU 2018-14 is effective for the Company for the year ended December 26, 2020. The Company adopted ASU 2018-14 in the fourth quarter of 2020 and the impact of the adoption was not material to the Company's consolidated financial statements.

In August 2020, the FASB issued ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity's Own Equity (Subtopic 815-40). The ASU simplifies accounting for convertible instruments by removing major separation models required under current GAAP. Consequently, more convertible debt instruments will be reported as a single liability instrument with no separate accounting for embedded conversion features. This update removes certain settlement conditions that are required for equity contracts to qualify for the derivative scope exception, which will permit more equity contracts to qualify for it. This update also simplifies the diluted net income per share calculation in certain areas. The update is effective for annual and interim periods beginning after December 15, 2021, and early adoption is permitted for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. The Company is currently evaluating the impact the adoption of ASU 2020-06 would have on its consolidated financial statements.

In March 2020, the FASB issued ASU 2020-04 (Topic 848), "Reference Rate Reform - Facilitation of the Effects of Reference Rate Reform on Financial Reporting” (“ASU 2020-04”), which provides temporary optional expedients and exceptions to the existing guidance on contract modifications and hedge accounting to ease the financial reporting burdens related to the expected market transition from the London Interbank Offered Rate ("LIBOR") and other interbank offered rates to alternative reference rates, such as the Secured Overnight Financing Rate. The standard was effective upon issuance and may generally be applied through December 31, 2022 to any new or amended contracts, hedging relationships, and other transactions that reference LIBOR. The Company will apply the amendments when its relevant contracts are modified upon transition to alternative reference rates.

In December 2019, FASB issued ASU 2019-12, "Simplifying the Accounting for Income Taxes" (“ASU 2019-12”), as part of its simplification initiative. ASU 2019-12 removes certain exceptions from Accounting Standards Codification ("ASC") 740, "Income Taxes" ("ASC 740"), including (i) the exception to the incremental approach for intra period tax allocation when there is a loss from continuing operations and income or a gain from other items such as discontinued operations or other comprehensive income; (ii) the exception to accounting for outside basis differences of equity method investments and foreign subsidiaries; and (iii) the exception to limit tax benefit recognized in interim period in cases when the year-to-date losses exceeds anticipated losses. ASU 2019-12 also simplifies U.S. GAAP in several other areas of ASC 740 such as (i) franchise taxes and other taxes partially based on income; (ii) step-up in tax basis goodwill considered part of a