General rule for methods of accounting

Taxable income shall be computed under the method of accounting on the basis of which the taxpayer regularly computes his income in keeping his books. If no method of accounting has been regularly used by the taxpayer, or if the method used does not clearly reflect income, the computation of taxable income shall be made under such method as, in the opinion of the Secretary, does clearly reflect income. Subject to the provisions of subsections (a) and (b), a taxpayer may compute taxable income under any of the following methods of accounting— A taxpayer engaged in more than one trade or business may, in computing taxable income, use a different method of accounting for each trade or business. Except as otherwise expressly provided in this chapter, a taxpayer who changes the method of accounting on the basis of which he regularly computes his income in keeping his books shall, before computing his taxable income under the new method, secure the consent of the Secretary. If the taxpayer does not file with the Secretary a request to change the method of accounting, the absence of the consent of the Secretary to a change in the method of accounting shall not be taken into account—