D.C. Mun. Regs. tit. 17, § 3906
3906.
RECEIPTS
3906.1 Prior to the completion of the contracted work, a licensee that accepts any payment for the work shall promptly deliver to the property owner a receipt for that payment.
3906.2 If payment is made by check or U.S. Postal money order, no receipt need be delivered to the property owner.
Source: Final Rulemaking published at 56 DCR 3103 (April 24, 2009).