D.C. Mun. Regs. tit. 14 § 3826
The Office of Administrative Hearings or the Commission may impose simple interest on a rent refund ordered pursuant to § 901(a) of the Act (D.C. Official Code § 42-3509.01(a)) and §§ 4217.1 and 4217.2 of this title, or on an award of attorney's fees pursuant to § 902 of the Act (D.C. Official Code § 42-3509.02) and § 3825 of this chapter.
Interest shall accrue separately for each month for which a rent refund is ordered. The total interest imposed shall be the sum of the interest calculated for each rent overcharge in the rent refund order. If the total amount of a rent refund in any month results from multiple violations of the Act that arose on different dates, the interest on the refund owed shall be separately calculated for each violation, from the date of the violation.
The applicable interest rate imposed on a rent refund shall be the judgment interest rate used by the Superior Court of the District of Columbia pursuant to D.C. Official Code § 28-3302(c) on the date of the order to pay the refund.
The accrual period for interest on a rent refund shall be calculated from the date the unlawful rent was charged, which includes the date a service or facility was reduced without a corresponding reduction in rent, to the date of the order to pay the rent refund.
The interest accrued on a rent refund shall be the product of:
If the amount of a rent refund is modified by a subsequent order on reconsideration, appeal, or remand, the subsequent order shall include a recalculation of the total interest accrued through the date of the subsequent order. For the purposes of § 3826.3, "the date of the order to pay the refund" shall mean the date of the first order that imposed a rent refund, not the subsequent order.
If the Commission determines in an appeal that a final order of the Office of Administrative Hearings miscalculates the interest to be imposed on a rent refund but does not find error in the amount of the rent refund itself, the Commission may correct the calculation and impose interest in accordance with § 3826.6.
After a final order to pay a rent refund or attorney's fees is issued, interest shall accrue and be owed on any unpaid portion of the refund or fees, at the rate established by § 3826.3, until full payment is made. Interest imposed under this subsection shall be calculated on the total amount of a rent refund, not each separate rent overcharge or violation, and not including any interest calculated in the order. Payment of interest owed under this subsection may be enforced by filing an application for entry of the final order as a judgment in accordance with Superior Court Civil Rule 12-I(b)(1)(G) or by otherwise commencing a civil action in the Superior Court of the District of Columbia for enforcement of the final order pursuant to § 218 of the Act (D.C. Official Code § 42-3502.18) .
Interest shall not be imposed under this section on any rent overcharges that are deposited in an escrow account or court registry if the deposit bears interest.
D.C. Mun. Regs. Tit. 14, § 3826