New Mexico late fee law

15%per year

A cap on what an agreed rate may charge, not a rate that accrues by default. With no agreed rate, this figure gives you nothing to charge.

In the absence of a written contract fixing a different rate, interest 'shall be not more than fifteen percent annually' (a) on money due by contract, (b) on money received to the use of another and retained without the owner's consent, and (c) on money due upon the settlement of matured accounts from the day the balance is ascertained - 15% is thus the statutory default/ceiling applied when a contract is silent. Judgment interest is separate: 8.75% per year under NMSA § 56-8-4 (or the contract rate if the judgment is on a written contract fixing a rate; 15% for tortious/bad-faith/willful conduct). Text corroborated across multiple year-versions on Justia/FindLaw; official nmonesource text not fetched this session.

Section 56-8-3 applies only absent a written contract fixing a different rate, so parties may contract in writing for another rate. Secondary sources report New Mexico deregulated general usury limits for most commercial lending (leaving agreed rates subject mainly to unconscionability and specific consumer-lending statutes), but no current general usury-cap statute was verified this session - verify with counsel before relying on the absence of a cap.

public+private-construction

NM Prompt Payment Act (NMSA 57-28-1 through 57-28-11) applies to construction contracts on both public and private projects (residential projects of 4 or fewer units excluded): owners must pay undisputed pay requests within 21 days of receipt; contractors/subcontractors must pay their subs and suppliers within 7 days of receiving payment; late payments accrue interest at 1.5% of the undisputed amount per month or fraction of a month until paid.

No NM statute specific to flat late fees on commercial invoices was found; agreed late fees are enforceable subject to the liquidated-damages/penalty doctrine. Note § 56-8-3(C) independently allows up to 15% annual interest on matured accounts from the day the balance is ascertained even without an agreed late-charge clause.