An amount of adoption assistance paid to an adoptive parent in excess of the payment that was actually due is recoverable by the commissioner, even when the overpayment was caused by agency error or circumstances outside the responsibility and control of the parent or provider. Adoption assistance amounts covered by this section include basic maintenance needs payments, monthly supplemental maintenance needs payments, reimbursement of nonrecurring adoption expenses, reimbursement of special nonmedical costs, and reimbursement of medical costs.