N.M. Stat. § 58-19-10
The holder of a contract, upon request by the buyer, may extend the scheduled due date of all or any part of any installment or defer payment or renew or restate the unpaid time balance of such contract, the amount of the installments and the time schedule therefor and may collect for such extension, deferment, renewal or restatement a refinance charge computed at the discretion of the holder, under either of the following optional methods of computation at the rates indicated as follows:
OPTION 1. In the event one or more installments are extended, deferred or restated, the holder may compute an extension charge on the amount of the installment payment or payments or part thereof which is extended, for the period of time for which each payment, or part thereof is extended, deferred or restated, at the following rates on contracts originally in the respective classification of motor vehicles set forth in Section 8A of this act:
Class 1 | 1 percent per month |
Class 2 | 1 1/2 percent per month |
Class 3 and 4 | 2 percent per month |
Such extension charges may be computed on the basis of a full month for any fractional month period in excess of ten days.
OPTION 2. In the event the unpaid time balance of the contract is extended, deferred, renewed or restated, the holder may compute a refinance charge on such amount by adding to the unpaid time balance the cost for insurance and other benefits incidental to the refinancing plus any accrued delinquency and collection charges, and deducting any refund which may be due the buyer by prepayment pursuant to Section 9 [58-19-9 NMSA 1978] of the Motor Vehicle Sales Finance Act, at the rate of the finance charge specified in Section 8A of this act and by reclassifying the motor vehicle by its then year model, for the term of the refinancing agreement, but otherwise subject to the provisions of this act governing computation of the original finance charge. The provisions of this act governing minimum finance charges and acquisition costs under the refund schedule shall not apply in calculating refinance charges on the contract renewed under this method of computation.
NMS § 58-19-10