20 CFR 416.2045: Overpayments and underpayments; federally administered supplementation.

(a) Overpayments. Upon determination that an overpayment has been made, adjustments will be made against future federally administered State supplementary payments for which the person is entitled. Rules and requirements (see §§ 416.550 through 416.586) in effect for recovery (or waiver) of supplemental security income benefit overpayments shall also apply to the recovery (or waiver) of federally administered State supplementary overpaid amounts. If the overpaid person's entitlement to the State supplementary payments is terminated prior to recoupment of the overpaid State supplementary payment amount, and the overpayment cannot be recovered from a Federal benefit payable under this part, the person's record will be annotated (specifying the amount of the overpayment) to permit recoupment if the person becomes reentitled to supplementary payments of such State or to a Federal benefit under this part.

(b) Underpayments. Upon determination that an underpayment of State supplementary payments is due and payable, the underpaid amount shall be paid to the underpaid claimant directly, or his representative. If the underpaid person dies before receiving the underpaid amount of State supplementary payment the underpaid amount shall be paid to the claimant's eligible spouse. If the deceased claimant has no eligible spouse, no payment of the underpaid amount shall be made. (See §§ 416.538 through 416.543.)