D.C. Mun. Regs. tit. 9, r. 9-457
Parking lot operators and other vendors who sell or charge for the service of parking, storing, or keeping motor vehicles or trailers shall be able to fully substantiate any tax-free sales made.
In the case of tax-free sales made to persons who park on the premises where they reside, in accordance with § 455, the operator or other vendor shall keep a record of the date of sale, the name of the resident, the residential address of the resident, and the amount of the sale.
Vendors are required to keep records of tax-free sales to persons holding exemption cards which shall include the name of the purchaser, the date of sale, the amount of sale, and the exemption card number for each separate transaction.
If a sale or charge is made on a monthly basis, one record of the sale for the month is sufficient.
If a sale or charge is made on a daily basis, a separate record of that sale or charge shall be kept on a daily basis.
Vendors shall be responsible for honoring an exemption card for sales tax on parking only for the parking lot specified on the card and the motor vehicle described on the card.
D.C. Mun. Regs. tit. 9, r. 9-457