955 Mass. Reg. 2.07
If an agreement is prepaid in full by cash, by a new agreement or by refinancing of such agreement, the debtor shall receive a refund or credit of a portion of the precomputed interest charge. The amount of any such refund or credit shall represent at least as great a proportion of the total amount of the precomputed interest charge as the sum of the scheduled periodic total of payments after the date of prepayment, as the date of prepayment is fixed below bears to the sum of the scheduled periodic total of payment under the schedule of installments in the original agreement. Such computation of refund or credit shall be made under the so-called sum-of-the-digits method. If the prepayment is made other than on an installment due date, it shall be deem to have been made on the first installment due date if the prepayment occurs before that date, and in any other case it shall be deemed to have been made on the next preceding or next succeeding installment due date, whichever is nearer to the date of prepayment.
955 CMR 2.07