District of Columbia Code Division VIII. General Laws. § 47-1334. Interest rate.

(a) The rate of simple interest on all amounts due, owing, or paid for the taxes sold or bid off to the District under this chapter shall be 1.5% per month or portion thereof until paid, excluding surplus;  provided, that interest on the amount sold at tax sale, excluding surplus, shall accrue at the applicable interest rate beginning the first day of the month following the tax sale.  No interest shall accrue for surplus, expenses, or the reasonable value of improvements.

(b) The purchaser shall receive simple interest of 1.5% per month or portion thereof on the amount paid for the real property, excluding surplus, beginning on the first day of the month immediately following when the real property was sold or the certificate of sale was assigned by the Mayor until the payment to the Mayor is made as required under § 47-1361(a), by another purchaser under § 47-1382(c), or by the trustee under § 47-1382.01(d)(2), and as provided in § 47-1354(b) for the period when such other taxes were paid.  The purchaser shall receive no interest for expenses or the reasonable value of improvements.