I would advise to write the father with the following proposal: either you be allowed to treat the discrepancy as an off-set, you else you'll need to go back to court to enforce the arrears, in which case he'll be hit with interest and counsel fees. If he chooses the "hard way," then hire a lawyer & file the application. Speak to a Dutchess/Westchester Child Support lawyer for a full assessment.  -- David Bliven, Westchester Child Support lawyer (www.blivenlaw.net)