5 C.F.R. § 179.307
(b) Request for offset to a Federal agency: The Director or his or her designee may request that funds due and payable to a debtor by a Federal agency be administratively offset in order to collect a debt owned to OPM by that debtor. In requesting administrative offset OPM, as creditor, will certify in writing to the Federal agency holding funds of the debtor:
(c) Request for offset from a Federal agency: When administrative offset is authorized, any Federal creditor agency may request OPM to make an administrative offset from any OPM funds that are due and payable to a creditor agency's debtor. OPM shall initiate the requested administrative offset only upon:
(1) Receipt of written certification from the creditor agency: