Section 44National Internal Revenue Code of 1997 (Republic Act No. 8424), Sec. 44

Period in which Items of Gross Income Included. - The amount of all items of gross income shall be included in the gross income for the taxable year in which received by the taxpayer, unless, under methods of accounting permitted under Section 43, any such amounts are to be properly accounted for as of a different period. In the case of the death of a taxpayer, there shall be included in computing taxable income for the taxable period in which falls the date of his death, amounts accrued up to the date of his death if not otherwise properly includible in respect of such period or a prior period.