Interest on unpaid invoices in New Mexico: up to 15% a year if no rate was agreed; the most you can set depends on the deal

New Mexico's rate when no rate was agreed

Up to 15%. Without a written contract fixing a different rate, interest on money due by contract and on settled matured accounts is 'not more than fifteen percent annually' (a ceiling, not a fixed figure). Open accounts: no more than 15% a year, starting 30 days after delivery of the last article or service, unless the parties agree a higher rate (56-8-5).

• “The rate of interest, in the absence of a written contract fixing a different rate, shall be not more than fifteen percent annually in the following cases: A. on money due by contract; B. on money received to the use of another and retained without the owner's consent expressed or implied; and C. on money due upon the settlement of matured accounts from the day the balance is ascertained.” — NMSA 1978, § 56-8-3, read November 6, 2026
• “In current or open accounts there shall not be collected more than fifteen percent interest annually thereon, thirty days after the delivery of the last article or service; provided that the parties may set a higher rate by agreement.” — NMSA 1978, § 56-8-5, read November 6, 2026
• “Interest shall be allowed on judgments and decrees for the payment of money from entry and shall be calculated at the rate of eight and three-fourths percent per year, unless:” — NMSA 1978, § 56-8-4(A), read November 6, 2026

The most you can set in New Mexico

For a homeowner: It depends: see NMSA 56-8-5 and 56-8-9. No general numeric cap found in NMSA 56-8 for a written agreement: 56-8-9 allows only 'the rates permitted in Sections 56-8-1 through 56-8-21', and the old maximum-rate sections 56-8-11 to 56-8-11.4 are listed as Repealed. For open accounts, 56-8-5 caps interest at 15% 'provided that the parties may set a higher rate by agreement'.

For a business customer: No cap. No maximum-rate law applies where a corporation, LLC or other business entity is the debtor (56-8-9(B)).

• “Unless otherwise provided by law, no person, corporation or association, directly or indirectly, shall take, reserve, receive or charge any interest, discount or other advantage for the loan of money or credit or the forbearance or postponement of the right to receive money or credit except at the rates permitted in Sections 56-8-1 through 56-8-21 NMSA 1978.” — NMSA 1978, § 56-8-9(A), read November 6, 2026
• “56-8-11. Repealed. 56-8-11.1. Repealed. 56-8-11.2. Repealed. 56-8-11.3. Repealed. 56-8-11.4. Repealed.” — NMSA 1978, §§ 56-8-11 to 56-8-11.4 (table of sections), read November 6, 2026
• “No provision of law prescribing maximum rates of interest that may be charged in any transaction shall apply to a transaction in which a corporation, limited liability corporation or other business entity is a debtor, regardless of the purpose for which the corporation was formed and regardless of the fact that an individual is codebtor, endorser, guarantor, surety or accommodation party.” — NMSA 1978, § 56-8-9(B), read November 6, 2026

Late fees in New Mexico

What the text says: Retail installment contracts: if the contract provides, a delinquency and collection charge on an installment more than 10 days late of no more than 5% of the installment or $5, whichever is less (or instead, interest after maturity up to the highest lawful contract rate). Retail installment contracts (NMSA 56-1, Retail Installment Sales).

• “The holder of any retail installment contract, if it so provides, may collect a delinquency and collection charge on each installment in default for a period of more than ten days in the amount not to exceed five percent of each installment or five dollars ($5.00), whichever is less, or in lieu thereof, interest after maturity of each such installment not to exceed the highest lawful contract rate.” — NMSA 1978, § 56-1-2(K), read November 6, 2026

Does New Mexico want it agreed in advance?

Agreed in advance: New Mexico's text read does not say so in general. Retail installment delinquency charge only 'if it so provides'; open-account interest up to 15% needs no agreement and a higher rate needs one (56-8-5).

• “provided that the parties may set a higher rate by agreement.” — NMSA 1978, § 56-8-5, read November 6, 2026

Homeowners and businesses in New Mexico

Homeowner work on a home of 4 or fewer units is outside the Prompt Payment Act. Business-entity debtors have no maximum-rate protection at all (56-8-9(B)); individuals keep the 56-8 limits (15% on open accounts unless agreed higher).

• “The provisions of the Prompt Payment Act do not apply to construction contracts for residential property containing four or fewer dwelling units.” — NMSA 1978, § 57-28-3, read November 6, 2026

Prompt payment on private construction in New Mexico

See the state's words below. Does NOT apply to residential property with four or fewer dwelling units. Prompt Payment Act, NMSA 57-28 (the article titled Retainage).

• “If the owner fails to pay the contractor within twenty-one days after receipt of an undisputed request for payment, the owner shall pay interest to the contractor beginning on the twenty-second day after payment was due, computed at one and one-half percent of the undisputed amount per month or fraction of a month until the payment is issued.” — NMSA 1978, § 57-28-5(A), read November 6, 2026
• “The provisions of the Prompt Payment Act do not apply to construction contracts for residential property containing four or fewer dwelling units.” — NMSA 1978, § 57-28-3, read November 6, 2026

Work out a late charge in New Mexico

Set your own rate.

Check New Mexico's own text

Before you charge: read NMSA 1978, § 56-8-3 and the other New Mexico texts quoted on this page, or ask a lawyer. As of November 6, 2026.

This is a plain-words summary of each state's own laws as of November 6, 2026, not legal advice. Rules have exceptions. Check the state's own text, linked on every state's page, or a lawyer before you charge a late fee or interest.

Compare New Mexico with every state's answer, or with its neighbours just below.

Next door to New Mexico

• Arizona: 10% if none agreed, no general cap found
• Colorado: 8% if none agreed, depends by agreement
• Oklahoma: 6% if none agreed, depends by agreement
• Texas: 6% if none agreed, depends by agreement

Official sources for New Mexico

• NMSA 1978, § 56-8-3 — read November 6, 2026
• NMSA 1978, § 57-28-5(A) — read November 6, 2026

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