D.C. Code § 47-1804.03
The deductions and credits provided for in this chapter shall be taken for the taxable year in which "paid or accrued" or "paid or incurred", dependent upon the method of accounting upon the basis of which the net income is computed unless, in order to clearly reflect the income, the deductions or credits should be taken as of a different period. In the case of death of a taxpayer on the cash basis, no amount will be allowed as a deduction which was accrued up to the date of the taxpayer's death; and on the accrual basis, no amount (except amounts includible in computing a partner's net income) accrued only by reason of the death of the taxpayer shall be included in computing net income for the period in which falls the date of the taxpayer's death but such amounts shall be deductible by the estate or other person who paid them or is liable for their payment.
D.C. Code § 47-1804.03