D.C. Mun. Regs. tit. 8, r. 8-B3014
If a purchase order is terminated or cancelled, the CCO shall notify the contractor in writing that the purchase order has been terminated or cancelled.
If the contractor accepts the termination or cancellation and does not claim that costs were incurred as a result of starting performance, no further action shall be required and the purchase order shall be considered terminated or cancelled.
If the contractor does not accept the termination or cancellation or claims that costs were incurred as a result of starting performance, the CCO shall treat the action as a termination for default or convenience.
The CCO shall terminate or cancel purchase orders in writing by formal letter, electronic mail or by written modification.
D.C. Mun. Regs. tit. 8, r. 8-B3014