D.C. Mun. Regs. tit. 27, r. 27-1804
Each purchase order modification shall identify the order it modifies and shall contain an appropriate modification number.
The contracting officer shall obtain a contractor's written acceptance of a purchase order modification if the contracting officer determines the written acceptance necessary to ensure the contractor's compliance with the revised purchase order.
If a purchase order that has been accepted in writing by the contractor is to be terminated, the contracting officer shall process the termination action in accordance with the provisions of Chapter 37 of this title.
If a purchase order that has not been accepted in writing by the contractor is to be canceled, the contracting officer shall notify the contractor in writing that the purchase order has been canceled, request the contractor's written acceptance of the cancellation, and proceed in accordance with the provisions of §§ 1804.5 and 1804.6.
If the contractor accepts the cancellation and does not claim that costs were incurred as a result of beginning performance under the purchase order, no further action shall be required and the purchase order shall be considered canceled.
If the contractor does not accept the cancellation or claims that costs were incurred as a result of beginning performance under the purchase order, the contracting officer shall treat the action as a termination in accordance with the provisions of Chapter 37 of this title.
D.C. Mun. Regs. tit. 27, r. 27-1804