These financial statements are prepared in accordance with accounting principles generally accepted in the United States of America. The accompanying consolidated financial statements include our accounts and those of our subsidiaries in which we have a controlling interest. All significant intercompany accounts and transactions have been eliminated. Certain amounts in prior periods may have been reclassified to conform to the current period presentation. The effects of the reclassifications were not material to the consolidated financial statements.

The preparation of financial statements in conformity with generally accepted accounting principles requires the use of estimates and assumptions by management in determining the reported amounts of assets and liabilities, revenue and expenses and disclosures regarding contingent assets and liabilities. Actual results could differ from those estimates. The most significant estimates used in our financial statements affect revenue and cost recognition for construction contracts, the allowance for doubtful accounts, self-insurance accruals, deferred tax assets, warranty accruals, fair value accounting for acquisitions and the quantification of fair value for reporting units in connection with our goodwill impairment testing.

We consider all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents.

In February 2016, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2016-02, “Leases (Topic 842).” The standard requires substantially all leases (with the exception of leases with a term of one year or less) to be recorded on the Balance Sheet using a method referred to as the right-of-use (“ROU”) asset approach. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 and interim periods within those years. Full retrospective application is prohibited. We adopted ASU No. 2016-02, “Leases (Topic 842)”, on January 1, 2019, using

the transition method allowed by ASU No. 2018-11, “Leases (Topic 842) Targeted Improvements” in which lessees apply the new lease standard on the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. We adopted the practical expedient allowing us to not include leases with an initial term of 12 months or less on the Balance Sheet. Furthermore, we elected to apply the practical expedient allowing an entity to forgo reassessing (1) whether expired or existing contracts contain a lease, (2) classification of expired or existing leases, and (3) whether capitalized costs associated with expired or existing leases should be classified as “initial direct costs” under Topic 842. The adoption of ASU 2016-02 did not have a significant impact to our Statement of Operations or Cash Flows. The adoption of ASU 2016-02 resulted in the recording of right-of-use asset and lease liabilities of $75.9 million on our Balance Sheet as of January 1, 2019 but did not result in a cumulative-effect adjustment to retained earnings.

In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments – Credit Losses (Topic 326).” The standard requires companies to consider historical experiences, current market conditions and reasonable and supportable forecasts in the measurement of expected credit losses. The standard will require us to accrue higher credit losses on financial assets compared to the current guidance on various items, such as contract assets and current receivables. We are still completing our evaluation of the impact of this authoritative guidance on our consolidated financial statements, but expect that it will increase our allowances for credit losses upon adoption. ASU 2016-13 is effective for fiscal years beginning after December 15, 2019 and interim periods within those years. Early adoption is permitted.

In August 2018, the FASB issued ASU No. 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework — Changes to the Disclosure Requirements for Fair Value Measurement.” This standard removes certain disclosure requirements including the valuation processes for Level 3 fair value measurements, the policy for timing of transfers between levels and the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy. The standard requires certain additional disclosures for public entities, including disclosure of the changes in unrealized gains and losses included in Other Comprehensive Income for Level 3 fair value measurements and the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. ASU 2018-13 is effective for fiscal years beginning after December 15, 2019 and interim periods within those years. Certain amendments, including the amendment on changes in unrealized gains and losses and the range and weighted average of significant unobservable inputs, should be applied prospectively while other amendments should be applied retrospectively to all periods presented upon their effective date. We are currently evaluating the potential impact of this authoritative guidance on our consolidated financial statements.

In December 2019, the FASB issued ASU No. 2019-12, “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes.” This standard simplifies the accounting for income taxes by eliminating certain exceptions to the guidance in Topic 740 related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. The standard also simplifies aspects of the accounting for franchise taxes and enacted changes in tax laws or rates and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. ASU 2019-12 is effective for fiscal years beginning after December 15, 2020 and interim periods within that year. Early adoption is permitted. We are currently evaluating the potential impact of this authoritative guidance on our consolidated financial statements.

Revenue is recognized when control of the promised goods or services is transferred to our customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. Sales-based taxes are excluded from revenue.

We provide mechanical and electrical contracting services. Our mechanical segment principally includes HVAC, plumbing, piping and controls, as well as off‑site construction, monitoring and fire protection. Our electrical segment includes installation and servicing of electrical systems. We install, maintain, repair and replace products and systems throughout the United States. All of our revenue is recognized over time as we deliver goods and services to our customers. Revenue can be earned based on an agreed upon fixed price or based on actual costs incurred marked up at an agreed upon percentage.

For fixed price agreements, we use the percentage of completion method of accounting under which contract revenue recognizable at any time during the life of a contract is determined by multiplying expected total contract

revenue by the percentage of contract costs incurred at any time to total estimated contract costs. More specifically, as part of the negotiation and bidding process to obtain installation contracts, we estimate our contract costs, which include all direct materials, labor and subcontract costs and indirect costs related to contract performance, such as indirect labor, supplies, tools, repairs and depreciation costs. These contract costs are included in our results of operations under the caption “Cost of Services.” Then, as we perform under those contracts, we measure costs incurred, compare them to total estimated costs to complete the contract and recognize a corresponding proportion of contract revenue. Labor costs are considered to be incurred as the work is performed. Subcontractor labor is recognized as the work is performed. Non‑labor project costs consist of purchased equipment, prefabricated materials and other materials. Purchased equipment on our projects is substantially produced to job specifications and is a value-added element to our work. The costs are considered to be incurred when title is transferred to us, which typically is upon delivery to the work site. Prefabricated materials, such as ductwork and piping, are generally performed at our shops and recognized as contract costs when fabricated for the unique specifications of the job. Other materials costs are generally recorded when delivered to the work site. This measurement and comparison process requires updates to the estimate of total costs to complete the contract, and these updates may include subjective assessments and judgments.

We account for a contract when: (i) it has approval and commitment from both parties, (ii) the rights of the parties are identified, (iii) payment terms are identified, (iv) the contract has commercial substance, and (v) collectability of consideration is probable. We consider the start of a project to be when the above criteria have been met and we either have written authorization from the customer to proceed or an executed contract.

Selling, marketing and estimation costs incurred in relation to selling contracts are expensed as incurred. On rare occasions, we may incur significant expenses related to selling a contract that we only incurred because we sold that contract. If this occurs, we capitalize that cost and amortize it on a percentage of completion basis over the life of the contract. We do not currently have any capitalized selling, marketing, or estimation costs on our Balance Sheet and did not incur any impairment loss in the current year.

We generally do not incur significant incremental costs related to obtaining or fulfilling a contract prior to the start of a project. On rare occasions, when significant pre-contract costs are incurred, they are capitalized and amortized on a percentage of completion basis over the life of the contract. We do not currently have any capitalized obtainment or fulfillment costs on our Balance Sheet and did not incur any impairment loss on such costs in the current year.

Project contracts typically provide for a schedule of billings or invoices to the customer based on our job-to-date percentage of completion of specific tasks inherent in the fulfillment of our performance obligation(s). The schedules for such billings usually do not precisely match the schedule on which costs are incurred. As a result, contract revenue recognized in our Statement of Operations can and usually does differ from amounts that can be billed or invoiced to the customer at any point during the contract. Amounts by which cumulative contract revenue recognized on a contract as of a given date exceed cumulative billings and unbilled receivables to the customer under the contract are reflected as a current asset in our Balance Sheet under the caption “Costs and estimated earnings in excess of billings.” Amounts by which cumulative billings to the customer under a contract as of a given date exceed cumulative contract revenue recognized on the contract are reflected as a current liability in our Balance Sheet under the caption “Billings in excess of costs and estimated earnings.”

Accounts receivable include amounts billed to customers under retention or retainage provisions in construction contracts. Such provisions are standard in our industry and usually allow for a small portion of progress billings or the contract price to be withheld by the customer until after we have completed work on the project, typically for a period of six months. Based on our experience with similar contracts in recent years, the majority of our billings for such retention balances at each Balance Sheet date are finalized and collected within the subsequent year. Retention balances at December 31, 2019 and 2018 were $111.7 million and $80.8 million, respectively, and are included in accounts receivable.

Accounts payable at December 31, 2019 and 2018 included $15.8 million and $13.7 million of retainage under terms of contracts with subcontractors, respectively. The majority of the retention balances at each Balance Sheet date are finalized and paid within the subsequent year.

The percentage of completion method of accounting is also affected by changes in job performance, job conditions, and final contract settlements. These factors may result in revisions to estimated costs and, therefore, revenue. Such revisions are frequently based on further estimates and subjective assessments. The effects of these revisions are recognized in the period in which revisions are determined. When such revisions lead to a conclusion that a loss will be recognized on a contract, the full amount of the estimated ultimate loss is recognized in the period such conclusion is reached, regardless of the percentage of completion of the contract.

Revisions to project costs and conditions can give rise to change orders under which there is an agreement between the customer and us that the customer pays an additional or reduced contract price. Revisions can also result in claims we might make against the customer to recover project variances that have not been satisfactorily addressed through change orders with the customer. Except in certain circumstances, we do not recognize revenue or margin based on change orders or claims until they have been agreed upon with the customer. The amount of revenue associated with unapproved change orders and claims was immaterial for the year ended December 31, 2019.

Variations from estimated project costs could have a significant impact on our operating results, depending on project size, and the recoverability of the variation via additional customer payments.

We typically invoice our customers with payment terms of net due in 30 days. It is common in the construction industry for a contract to specify more lenient payment terms allowing the customer 45 to 60 days to make their payment. It is also common for the contract in the construction industry to specify that a general contractor is not required to submit payments to a subcontractor until it has received those funds from the owner or funding source. In most instances, we receive payment of our invoices between 30 to 90 days of the date of the invoice.

A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC Topic 606. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied.

To determine the proper revenue recognition method for contracts, we evaluate whether two or more contracts should be combined and accounted for as one performance obligation and whether the combined or single contract should be accounted for as more than one performance obligation. This evaluation requires significant judgment and the decision to combine a group of contracts or separate the combined or single contract into multiple performance obligations could change the amount of revenue and profit recorded in a given period. For most of our contracts, the customer contracts with us to provide a significant service of integrating a complex set of tasks and components into a single project or capability (even if that single project results in the delivery of multiple units). Hence, the entire contract is accounted for as one performance obligation. Less commonly, however, we may promise to provide distinct goods or services within a contract, in which case we separate the contract into more than one performance obligation. If a contract is separated into more than one performance obligation, we allocate the total transaction price to each performance obligation in an amount based on the estimated relative standalone selling prices of the promised goods or services underlying each performance obligation. We infrequently sell standard products with observable standalone sales. In such cases, the observable standalone sales are used to determine the standalone selling price. More frequently, we sell a customized, customer-specific solution, and, in these cases, we typically use the expected cost plus a margin approach to estimate the standalone selling price of each performance obligation.

We recognize revenue over time for all of our services as we perform them because (i) control continuously transfers to that customer as work progresses, and (ii) we have the right to bill the customer as costs are incurred. The customer typically controls the work in process, as evidenced either by contractual termination clauses or by our rights to payment for work performed to date plus a reasonable profit to deliver products or services that do not have an alternative use to the Company.

For the reasons listed above, revenue is recognized based on the extent of progress towards completion of the performance obligation. The selection of the method to measure progress towards completion requires judgment and is based on the nature of the products or services to be provided. We generally use the cost to cost measure of progress for our contracts, as it best depicts the transfer of assets to the customer that occurs as we incur costs on our contracts. Under the cost to cost measure of progress, the extent of progress towards completion is measured based on the ratio of costs incurred to date to the total estimated costs at completion of the performance obligation. Revenue, including estimated fees or profits, is recorded proportionally as costs are incurred. Costs to fulfill include labor, materials and subcontractors’ costs, other direct costs and an allocation of indirect costs.

In our mechanical segment, for a small portion of our business in which our services are delivered in the form of service maintenance agreements for existing systems to be repaired and maintained, as opposed to constructed, our performance obligation is to maintain the customer’s mechanical system for a specific period of time. Similar to jobs, we recognize revenue over time; however, for service maintenance agreements in which the full cost to provide services may not be known, we generally use an input method to recognize revenue, which is based on the amount of time we have provided our services out of the total time we have been contracted to perform those services.

Due to the nature of the work required to be performed on many of our performance obligations, the estimation of total revenue and cost at completion (the process described below in more detail) is complex, subject to many variables and requires significant judgment. The consideration to which we are entitled on our long-term contracts may include both fixed and variable amounts. Variable amounts can either increase or decrease the transaction price. A common example of variable amounts that can either increase or decrease contract value are pending change orders that represent contract modifications for which a change in scope has been authorized or acknowledged by our customer, but the final adjustment to contract price is yet to be negotiated. Other examples of positive variable revenue include amounts awarded upon achievement of certain performance metrics, program milestones or cost of completion date targets and can be based upon customer discretion. Variable amounts can result in a deduction from contract revenue if we fail to meet stated performance requirements, such as complying with the construction schedule.

Contracts are often modified to account for changes in contract specifications and requirements. We consider contract modifications to exist when the modification either creates new or changes the existing enforceable rights and obligations. Most of our contract modifications are for goods or services that are not distinct from the existing performance obligation(s). The effect of a contract modification on the transaction price, and our measure of progress for the performance obligation to which it relates, is recognized as an adjustment to revenue (either as an increase or decrease) on a cumulative catchup basis.

We have a Company-wide policy requiring periodic review of the Estimate at Completion in which management reviews the progress and execution of our performance obligations and estimated remaining obligations. As part of this process, management reviews information including, but not limited to, any outstanding key contract matters, progress towards completion and the related program schedule, identified risks and opportunities and the related changes in estimates of revenue and costs. The risks and opportunities include management's judgment about the ability and cost to achieve the schedule (e.g., the number and type of milestone events), technical requirements (e.g., a newly developed product versus a mature product) and other contract requirements. Management must make assumptions and estimates regarding labor productivity and availability, the complexity of the work to be performed, the availability of materials, the length of time to complete the performance obligation (e.g., to estimate increases in wages and prices for materials and related support cost allocations), execution by our subcontractors, the availability and timing of funding from our customer, and overhead cost rates, among other variables.

Based on this analysis, any adjustments to revenue, cost of services, and the related impact to operating income are recognized as necessary in the quarter when they become known. These adjustments may result from positive program performance if we determine we will be successful in mitigating risks surrounding the technical, schedule and cost aspects of those performance obligations or realizing related opportunities and may result in an increase in operating income during the performance of individual performance obligations. Likewise, if we determine we will not be successful in mitigating these risks or realizing related opportunities, these adjustments may result in a decrease in

operating income. Changes in estimates of revenue, cost of services and the related impact to operating income are recognized quarterly on a cumulative catchup basis, meaning we recognize in the current period the cumulative effect of the changes on current and prior periods based on a performance obligation's percentage of completion. A significant change in one or more of these estimates could affect the profitability of one or more of our performance obligations. For projects in which estimates of total costs to be incurred on a performance obligation exceed total estimates of revenue to be earned, a provision for the entire loss on the performance obligation is recognized in the period the loss is determined.

The Company typically does not incur any returns, refunds, or similar obligations after the completion of the performance obligation since any deficiencies are corrected during the course of the work or are included as a modification to revenue. The Company does offer an industry standard warranty on our work, which is most commonly for a one-year period. The vendors providing the equipment and materials are responsible for any failures in their product unless installed incorrectly. We include an estimated amount to cover estimated warranty expense in our Cost of Services and record a liability on our Balance Sheet to cover our current estimated outstanding warranty obligations.

Prior to implementing ASC 606 on January 1, 2018, our methods for recognizing revenue were very similar to our current method under ASC 606. We used the actual cost as a percent of total expected cost at completion to estimate our percentage complete on fixed price jobs, a mark-up of costs for jobs in which revenue was based on time and materials incurred and elapsed time for those service maintenance contracts in which the full cost to provide the services cannot be reasonably estimated. Furthermore, our process for allocating transaction price to performance obligations is also substantially similar to prior years when, in most cases, a contract is one performance obligation. In those cases in which a contract is determined to have more than one performance obligation, the contract price is allocated to each performance obligation based on its standalone sales price.

During the years ended December 31, 2018 and December 31, 2019, net revenue recognized from our performance obligations satisfied in previous periods was not material.

Our consolidated 2019 revenue was derived from contracts to provide service activities in the mechanical and electrical services segments we serve. Refer to Note 14 – Segment Information for additional information on our reportable segments. We disaggregate our revenue from contracts with customers by activity, customer type and contract type, as we believe it best depicts how the nature, amount, timing and uncertainty of our revenue and cash flows are affected by economic factors. See details in the following tables (dollars in thousands):

Accounts Receivable include amounts from work completed in which we have billed or have an unconditional right to bill our customers. The amounts due are stated at their net estimated realizable value. We maintain an allowance for doubtful accounts to provide for the estimated amount of receivables that will not be collected. The allowance is based upon an assessment of customer creditworthiness, historical payment experience, the age of outstanding receivables and collateral to the extent applicable.

Contract assets include unbilled amounts typically resulting from sales under long term contracts when the cost to cost method of revenue recognition is used, revenue recognized exceeds the amount billed to the customer and right to payment is conditional, subject to completing a milestone, such as a phase of the project. Contract assets are generally classified as current.

Contract liabilities consist of advance payments and billings in excess of revenue recognized. Our contract assets and liabilities are reported in a net position on a contract by contract basis at the end of each reporting period. We classify advance payments and billings in excess of revenue recognized as current. It is very unusual for us to have advanced payments with a term of greater than one year; therefore, our contract assets and liabilities are usually all current. If we have advanced payments with a term greater than one year, the noncurrent portion of advanced payments would be included in other long-term liabilities in our consolidated Balance Sheets.

The following table presents the changes in contract assets and contract liabilities (in thousands):


	Year Ended December 31,
	2019				2018
	Contract		Contract		Contract		Contract
	Assets		Liabilities		Assets		Liabilities
Balance at beginning of period	$	10,213	$	130,986	$	30,116	$	106,005
Change due to acquisitions / disposals		6,573		31,556		2,833		8,195
Change due to conditional versus unconditional		(14,050)		—		6,244		—
Reclassified to unbilled accounts receivable		—		—		(28,980)		—
Change in timing for performance obligation to be satisfied		—		4,376		—		16,786
Balance at end of period	$	2,736	$	166,918	$	10,213	$	130,986

During the years ended December 31, 2019 and 2018, we recognized revenue of $126.7 million and $97.6 million related to our contract liabilities at January 1, 2019 and January 1, 2018, respectively.

We did not have any impairment losses recognized on our receivables or contract assets in 2019 and 2018.

Remaining construction performance obligations represent the remaining transaction price of firm orders for which work has not been performed and excludes unexercised contract options. As of December 31, 2019, the aggregate amount of the transaction price allocated to remaining performance obligations was $1.60 billion. The Company expects to recognize revenue on approximately 85% of the remaining performance obligations over the next 12 months, with the remaining recognized thereafter. Our service maintenance agreements are generally one-year renewable agreements.

We have adopted the practical expedient that allows us to not include service maintenance contracts less than one year, therefore we do not report unfulfilled performance obligations for service maintenance agreements.

We lease certain facilities, vehicles and equipment under noncancelable operating leases. The most significant portion of these noncancelable operating leases are for the facilities occupied by our corporate office and our operating locations. Leases with an initial term of 12 months or less are not recorded on the Balance Sheet. We account for lease components separately from the non-lease components. We have certain leases with variable payments based on an index as well as some short-term leases on equipment and facilities. Variable lease expense and short-term lease expense were not material to our financial statements and aggregated to $8.4 million in 2019. Lease right-of-use assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of our leases do not provide an implicit rate, we generally use our incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The weighted average discount rate as of December 31, 2019 was 3.9%. We recognize lease expense, including escalating lease payments and lease incentives, on a straight-line basis over the lease term. Lease expense for the years ended December 31, 2019, 2018 and 2017 was $24.8 million, $23.4 million and $21.1 million respectively.

The lease terms generally range from three to ten years. Some leases include one or more options to renew, with renewal terms that can extend the lease term. We include the exercise of lease renewal options in the lease term when it is reasonably certain that we will exercise the option and such exercise is at our sole discretion. The weighted average remaining lease term was 8.1 years at December 31, 2019.

A majority of the Company’s real property leases are with individuals or entities with whom we have no other business relationship. However, in certain instances the Company enters into real property leases with current or former employees. Rent paid to related parties for the years ended December 31, 2019, 2018 and 2017 was approximately $3.7 million, $4.8 million and $4.8 million, respectively.

If we decide to cancel or terminate a lease before the end of its term, we would typically owe the lessor the remaining lease payments under the term of the lease. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants. On rare occasions, we rent or sublease certain real estate assets that we no longer use to third parties.

The following table summarizes the lease assets and liabilities included in the consolidated Balance Sheet as follows (in thousands):

The maturities of lease liabilities as of December 31, 2019 are as follows (in thousands):

The following table represents future minimum rental payments under noncancelable operating leases under ASC 840 as of December 31, 2018 (in thousands):

Inventories consist of parts and supplies that we purchase and hold for use in the ordinary course of business and are stated at the lower of cost or net realizable value using the average-cost method.

Property and equipment are stated at cost, and depreciation is computed using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are capitalized and amortized over the lesser of the expected life of the lease or the estimated useful life of the asset.

Expenditures for repairs and maintenance are charged to expense when incurred. Expenditures for major renewals and betterments, which extend the useful lives of existing equipment, are capitalized and depreciated over the remaining useful life of the equipment. Upon retirement or disposition of property and equipment, the cost and related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized in “Gain on sale of assets” in the Statement of Operations.

Goodwill is the excess of purchase price over the fair value of the net assets of acquired businesses. We assess goodwill for impairment each year, and more frequently if circumstances suggest an impairment may have occurred.

When the carrying value of a given reporting unit exceeds its fair value, a goodwill impairment loss is recorded for this difference, not to exceed the carrying amount of goodwill. If other reporting units have had increases in fair value, such increases may not be recorded. Accordingly, such increases may not be netted against impairments at other reporting units. The requirements for assessing whether goodwill has been impaired involve market-based information. This information, and its use in assessing goodwill, entails some degree of subjective assessment.

We perform our annual impairment testing as of October 1 and any impairment charges resulting from this process are reported in the fourth quarter. We segregate our operations into reporting units based on the degree of operating and financial independence of each unit and our related management of them. We perform our annual goodwill impairment testing at the reporting unit level. We perform a goodwill impairment review for each of our operating units, as we have determined that each of our operating units are reporting units.

In the evaluation of goodwill for impairment, we have the option to first assess qualitative factors to determine whether the existence of events or circumstances lead to a determination that it is more likely than not that the fair value of one of our reporting units is greater than its carrying value. If, after completing such assessment, we determine it is

more likely than not that the fair value of a reporting unit is greater than its carrying amount, then there is no need to perform any further testing. If we conclude otherwise, then we calculate the fair value of the reporting unit and compare the fair value with the carrying value of the reporting unit.

We estimate the fair value of the reporting unit based on a market approach and an income approach, which utilizes discounted future cash flows. Assumptions critical to the fair value estimates under the discounted cash flow model include discount rates, cash flow projections, projected long-term growth rates and the determination of terminal values. The market approach utilizes market multiples of invested capital from comparable publicly traded companies (“public company approach”). The market multiples from invested capital include revenue, book equity plus debt and earnings before interest, provision for income taxes, depreciation and amortization (“EBITDA”).

We amortize identifiable intangible assets with finite lives over their useful lives. Changes in strategy and/or market condition may result in adjustments to recorded intangible asset balances or their useful lives.

Long-lived assets are comprised principally of goodwill, identifiable intangible assets, property and equipment, and deferred tax assets. We periodically evaluate whether events and circumstances have occurred that indicate that the remaining balances of these assets may not be recoverable. We use estimates of future income from operations and cash flows, as well as other economic and business factors, to assess the recoverability of these assets.

We recognize assets acquired and liabilities assumed in business combinations, including contingent assets and liabilities, based on fair value estimates as of the date of acquisition.

Contingent Consideration—In certain acquisitions, we agree to pay additional amounts to sellers contingent upon achievement by the acquired businesses of certain predetermined profitability targets. We have recognized liabilities for these contingent obligations based on their estimated fair value at the date of acquisition with any differences between the acquisition date fair value and the ultimate settlement of the obligations being recognized in income from operations.

Contingent Assets and Liabilities—Assets and liabilities arising from contingencies are recognized at their acquisition date fair value when their respective fair values are determinable. Acquisition date fair value estimates are revised as necessary if, and when, additional information regarding these contingencies becomes available to further define and quantify assets acquired and liabilities assumed.

We are substantially self-insured for workers’ compensation, employer’s liability, auto liability, general liability and employee group health claims, in view of the relatively high per-incident deductibles we absorb under our insurance arrangements for these risks. Losses are estimated and accrued based upon known facts, historical trends and industry averages. Estimated losses in excess of our deductible, which have not already been paid, are included in our accrual with a corresponding receivable from our insurance carrier. Loss estimates associated with the larger and longer-developing risks—workers’ compensation, auto liability and general liability—are reviewed by a third-party actuary quarterly. Our self-insurance arrangements are further discussed in Note 11 “Commitments and Contingencies.”

We typically warrant labor for the first year after installation on new MEP systems that we build and install, and we pass through to the customer manufacturers’ warranties on equipment. We generally warrant labor for thirty days after servicing existing MEP systems. A reserve for warranty costs is estimated and recorded based upon the historical level of warranty claims and management’s estimate of future costs.

We conduct business throughout the United States in virtually all fifty states. Our effective tax rate changes based upon our relative profitability, or lack thereof, in states with varying tax rates and rules. In addition, discrete items such as tax law changes, judgments and legal structures can impact our effective tax rate. These items can also include the tax treatment for impairment of goodwill and other intangible assets, changes in fair value of acquisition-related assets and liabilities, tax reserves for uncertain tax positions, accounting for losses associated with underperforming operations and noncontrolling interests.

Income taxes are provided for under the liability method, which takes into account differences between financial statement treatment and tax treatment of certain transactions. Deferred taxes are based on the difference between the financial reporting and tax basis of assets and liabilities. The deferred tax provision represents the change during the reporting period in the deferred tax assets and deferred tax liabilities, net of the effect of acquisitions and dispositions. Deferred tax assets include tax loss and credit carryforwards and are reduced by a valuation allowance if, based on available evidence, it is more-likely-than-not some portion or all of the deferred tax assets will not be realized.

We regularly evaluate valuation allowances established for deferred tax assets for which future realization is uncertain. We perform this evaluation quarterly. In assessing the realizability of deferred tax assets, we must consider whether it is more-likely-than-not some portion, or all, of the deferred tax assets will not be realized. We consider all available evidence, both positive and negative, in determining whether a valuation allowance is required. Such evidence includes the scheduled reversal of deferred tax liabilities, projected future taxable income, taxable income in prior carryback years and tax planning strategies in making this assessment, and judgment is required in considering the relative weight of negative and positive evidence.

Significant judgment is required in assessing the timing and amounts of deductible and taxable items. We establish reserves when, despite our belief that our tax return positions are supportable, we believe that certain positions may be disallowed. When facts and circumstances change, we adjust these reserves through our provision for income taxes.

To the extent interest and penalties may be assessed by taxing authorities on any underpayment of income tax, such amounts have been accrued and are classified as a component in provision for income taxes in our Consolidated Statements of Operations.

We provide services in a broad range of geographic regions. Our credit risk primarily consists of receivables from a variety of customers including general contractors, property owners and developers and commercial and industrial companies. We are subject to potential credit risk related to changes in business and economic factors throughout the United States within the nonresidential construction industry. However, we are entitled to payment for work performed and have certain lien rights in that work. Further, we believe that our contract acceptance, billing and collection policies are adequate to manage potential credit risk. We regularly review our accounts receivable and estimate an allowance for uncollectible amounts. We have a diverse customer base, with our top customer representing 5% of consolidated 2019 revenue.

Our financial instruments consist of cash and cash equivalents, accounts receivable, other receivables, accounts payable, life insurance policies, notes to former owners, a revolving credit facility and a term loan. We believe that the carrying values of these instruments on the accompanying Balance Sheets approximate their fair values.

We recorded a $4.8 million gain in the fourth quarter of 2019 due to insurance proceeds we received in the fourth quarter related to the ransomware incident that occurred in April 2019. Approximately $1.6 million of the gain was recorded as a reduction in SG&A, and the remainder was recorded as a reduction in Cost of Services expense. These proceeds related to recoverable costs that were primarily incurred prior to the fourth quarter in 2019. We do not expect any additional insurance proceeds or other recoveries related to the ransomware incident.