# Accounting periods and methods IRS Publication 538 (Rev. January 2022). Governs fiscal years, periods, and the consistency of method. ## IRS Publication 538 Source: Retrieved: 2026-10-13 SHA-256 of the retrieved file (`p538.txt`): `dfaf00c55253ef28c3311e6767230365b60e13c22c87a87bb6a6bcc41bd2fa06` **Tax year** > A tax year is an annual accounting period for keeping records and reporting income and expenses. **Calendar year** > A calendar year is 12 consecutive months beginning on January 1st and ending on December 31st. **Fiscal year** > A fiscal year is 12 consecutive months ending on the last day of any month except December 31st. **Accounting methods** > No single accounting method is required of all taxpayers. You must use a system that clearly reflects your income and expenses and you must maintain records that will enable you to file a correct return. In addition to your permanent accounting books, you must keep any other records necessary to support the entries on your books and tax returns. You must use the same accounting method from year to year. **Accrual method** > Under an accrual method of accounting, you generally report income in the year it is earned and deduct or capitalize expenses in the year incurred.