D.C. Mun. Regs. tit. 27, r. 27-3311
The contracting officer shall identify and exclude from each billing, claim, and proposal costs that are expressly unallowable under this chapter or mutually agreed to be unallowable under an advance cost agreement.
When costs are identified as unallowable or mutually agreed to be unallowable, all directly associated costs shall also be unallowable.
Costs and directly associated costs specifically designated as unallowable as a result of a written decision by a contracting officer shall be identified when included in or used in computing any billing, claim, or proposal applicable to a District contract.
The contracting officer shall require records as support for claims, billings, and proposals that are adequate to establish and maintain visibility of those costs and directly associated costs which have been identified as unallowable.
The contracting officer shall identify unallowable costs involved in determining rates used for standard costs, indirect cost proposals, or billings at the time rates are proposed, established, revised, or adjusted.
D.C. Mun. Regs. tit. 27, r. 27-3311