If funds have been determined excess, but have already canceled, can the contracting officer issue a modification deobligating those funds.
Closed/Canceled accounts are those with balances that have been canceled under sections 1552, 1555, or 1557 of title 31 United States Code. When balances are canceled the amounts are not available for obligation or expenditure for any purpose.
Accounts that have been canceled/closed are only available for adjustments for recording keeping purposes. An adjustment is defined in the DoD Financial Management Regulation (FMR) as an increase or decrease to obligations or expenditures. Adjustment involves recording obligations or expenditures that were made or incurred, but not recorded, during the period prior to expiration or cancellation of the account.
Source: DoD Financial Management Regulation, Volume 3, Chapter 10