Annual Accounting Period
i.    441(c): defines the annual accounting period in which a taxpayer regularly computes income in keeping his records.  The annual period becomes the taxpayer’s taxable year and may be either a calendar or fiscal year.
1.    a calendar year commonly used by individual taxpayers is the 12 month period ending on December 31
2.    a fiscal year, more used by business, is the 12 month period ending on any month other than December.
a.    w/ a fiscal year the accounting needs to be filed in 4 months, 15 days after the fiscal year ends (60-72(a))
3.    Reg: 1.451-3:  in some instances, such as a long term construction contract, income and expenses may be reported under either the completed contract method or the percentage of completion method.
4.    172:  permits business losses (net operating loss) to be carried back two years and forward 20 years permitting current losses to be deducted form income arising in the earlier or later period.
5.    the claim of right doctrine:
a.    when a taxpayer reports income in one year and in the next determines that they had no right to the payment and is required to repay the money.
b.    The court in United States v. Lewis (1951), stated that the previous years was not to be disturbed but the new year allowed a deduction for the money repaid.