Mississippi late fee law

8%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 legal rate of interest on all notes, accounts and contracts is 8% per annum, calculated according to the actuarial method, absent a written contract for a different (finance-charge) rate. Verified via FindLaw statute mirror and corroborated by Justia's current Mississippi Code; Mississippi has no freely fetchable official legislature statute site.

Written contracts may provide a finance charge ('contract rate'). For borrowers generally the ceiling is the greater of 10% per annum or 5% above the Federal Reserve discount rate on 90-day commercial paper. For business entities (partnerships, joint ventures, religious societies, unincorporated associations, corporations) - per the statute, on larger/business obligations (FindLaw summary: loans exceeding $2,500) - the ceiling rises to the greater of 15% per annum or 5% above the discount rate, and the statute bars such business borrowers from asserting a usury claim or defense. Other statutes authorize higher rates for specific regulated credit.

public+private-construction

Public purchases: Miss. Code § 31-7-305 - if a public body does not mail payment within 45 days of receipt/inspection/approval of the invoice and goods/services (30 days after settling a dispute), it is liable for interest at 1.5% per month or portion thereof on the unpaid balance; § 31-5-27 addresses interest on delinquent public-works accounts. Private construction: § 87-7-3 - partial/progress/interim payments on non-public construction contracts not paid within 30 calendar days of the contractual due date bear interest at 1% per month from the due date until fully paid. No general prompt-payment statute for ordinary private non-construction B2B invoices was found.

No Mississippi statute specific to flat late fees on ordinary B2B trade invoices was found; the default reasonableness/liquidated-damages analysis applies. A late charge that operates as a finance charge should fit within the § 75-17-1 ceilings unless the business-borrower provision applies (which also bars the usury defense for those entities).