Figure taxable income using the method of accounting regularly used in keeping the estate's or trust's books and records. Generally, permissible methods include the cash method, the accrual method, or any other method authorized by the Internal Revenue Code. In all cases, the method used must clearly reflect income.
Generally, the estate or trust may change its accounting method (for income as a whole or for any material item) only by getting consent on Form 3115, Application for Change in Accounting Method. For more information, see Pub. 538, Accounting Periods and Methods.