Section 45National Internal Revenue Code of 1997 (Republic Act No. 8424), Sec. 45

Period for which Deductions and Credits Taken. - The deductions provided for in this Title shall be taken for the taxable year in which 'paid or accrued' or 'paid or incurred', dependent upon the method of accounting the basis of which the net income is computed, unless in order to clearly reflect the income, the deductions should be taken as of a different period. In the case of the death of a taxpayer, there shall be allowed as deductions 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 allowable in respect of such period or a prior period.