Method of accounting
(3) Method of accounting. Except as provided in paragraph (f)(2)(ii) of this section, a taxpayer's method of classifying contracts is a method of accounting under section 446 and, thus, may not be changed without the Commissioner's consent. If a taxpayer's method of classifying contracts is unreasonable, that classification method is an impermissible accounting method. A taxpayer may adopt any permissible method of accounting for each classification of contract. Such adoption is not a change in method of accounting under section 446 and the accompanying regulations. For example, a taxpayer that has had only contracts classified as nonexempt long-term contracts and has used the PCM for these contracts may adopt an exempt contract method in the taxable year it first enters into an exempt long-term contract. (4) Use of estimates(i) Estimating length of contract. A taxpayer must use a reasonable estimate of the time required to complete a contract when necessary to classify the contract (e.g., to determine whether the five-year completion rule for qualified ship contracts under 1.460-2(d), or the two-year completion rule for exempt construction contracts under 1.460-3(b), is satisfied, but not to determine whether a contract is completed within the contracting year under paragraph (b)(1) of this section). To be considered reasonable, an estimate of the time required to complete the contract must include anticipated time for delay, rework, change orders, technology or design problems, or other problems that reasonably can be anticipated considering the nature of the contract and prior experience. A contract term that specifies an expected completion or delivery date may be considered evidence that the taxpayer reasonably expects to complete or deliver the subject matter of the contract on or about the date specified, especially if the contract provides bona fide penalties for failing to meet the specified date. If a taxpayer classifies a contract based on a reasonable estimate of completion time, the contract will not be reclassified based on the actual (or another reasonable estimate of) completion time. A taxpayer's estimate of completion time will not be considered unreasonable if a contract is not completed within the estimated time primarily because of unforeseeable factors not within the taxpayer's control, such as third-party litigation, extreme weather conditions, strikes, or delays in securing permits or licenses. (ii) Estimating allocable contract costs. A taxpayer must use a reasonable estimate of total allocable contract costs when necessary to classify the contract (e.g., to determine whether a contract is a home construction contract under 1.460-(3)(b)(2)). If a taxpayer classifies a contract based on a reasonable estimate of total allocable contract costs, the contract will not be reclassified based on the actual (or another reasonable estimate of) total allocable contract costs.