The US government, especially the IRS, never forgets. If they think you owe them money they won't send you any until it is paid off. Your son needs to file a written appeal, through the mail, of the "offset" (their name for "we stole your money") through the procedures contained in the 'denial of surplus' letter. Step one, request an accounting of why they claim he owes them money from 2007. Once he knows why, he can still formally appeal their decision and he will receive a determination letter, or if he is lucky, a stimulus check.