GAO commented on its decision to withhold payment of a court award against the United States to offset a National Labor Relations Board (NLRB) administrative law judge's finding that the plaintiff owed back pay and severance to certain of its employees. GAO noted that the offset was proper, since: (1) there was mutuality between the parties; (2) the federal government, as the statutory enforcer of NLRB back pay awards, was the creditor for the purposes for those awards even though the plaintiff's employees were the ultimate beneficiaries; and (3) the back pay claim was liquidated or certain in amount, since it had been reduced to a sum certain by appropriate NLRB officials using a rational methodology.