Maryland late fee law

6%per year

Attaches to the debt by operation of law when you agreed no rate, so it accrues before any lawsuit and can be stated on a demand letter.

The Maryland Constitution provides that 'the Legal Rate of Interest shall be Six per cent per annum, unless otherwise provided by the General Assembly' (art. III, § 57), and Commercial Law § 12-102 implements it: except as otherwise provided by law, a person may not charge interest in excess of an effective rate of simple interest of 6% per annum on the unpaid principal balance of a loan. § 12-102 text verified on the official mgaleg.maryland.gov statute database; the constitutional provision corroborated via Justia's Maryland Constitution text and a Maryland Judiciary (mdcourts.gov) opinion headnote.

Yes. Com. Law § 12-103 permits higher rates: up to 8% simple interest under a written agreement signed by the borrower, and up to 18% (secured/unsecured non-savings collateral) or 24% (loans on or after July 1, 1982 meeting statutory conditions) in specified cases. Critically for B2B, Maryland usury limits effectively do not apply where the borrower is a corporation, or to commercial loans exceeding $15,000 not secured by residential real property, or commercial loans exceeding $75,000 secured by residential real property - such loans may bear any agreed rate.

public+private-construction

Public procurement: units must pay contractors within 30 days of the later of the contract due date or receipt of a proper invoice, and interest accrues at 9% per annum on undisputed amounts unpaid more than 45 days after invoice receipt (Md. Code, State Fin. & Proc. §§ 15-101 to 15-105; COMAR 21.07.01.18). Private construction: the Maryland construction prompt-pay provisions (Real Prop. §§ 9-301 to 9-305) require payment of undisputed amounts within 7 days of contract payment dates (or within 30 days of occupancy/possession if no dates set) and 7-day pass-through to subcontractors; they set payment deadlines but no special statutory penalty interest rate was verified for the private act. No act covering ordinary non-construction private commercial invoices was found.

No distinctive Maryland statute on flat late fees for commercial (non-consumer) invoices was found; the default rule applies - agreed late fees are enforceable if reasonable liquidated damages, not penalties. Interest-style finance charges on B2B accounts benefit from the § 12-103 corporate/commercial usury exemptions; charges to consumers are separately and strictly regulated.