D.C. Mun. Regs. r. 9-408
In addition to the provisions of the Act (D.C. Code § 47-2001(p)(2) ), the term "sales price," as used in the Act, shall not include any of the exceptions set forth in this section.
The amount of reimbursement of taxes paid by the purchaser to the vendor under the Act shall not be subject to the tax if the reimbursement amount is stated separately from the sales price.
The amount of federal retailer's excise taxes, if any, shall not be subject to the tax if the federal retailer's excise taxes are stated separately from the sales price.
The amount paid by any purchaser as interest, finance charge, or carrying charge shall not be subject to the tax if the amount of interest, finance charge, or carrying charge is stated separately from the amount paid for the tangible personal property or services.
D.C. Mun. Regs. r. 9-408