Reference · Missouri · 2026
Missouri late payment interest rate
When your contract sets no rate, the Missouri figure for interest on an overdue B2B invoice is 9%, under RSMo § 408.020.
On written contracts once due; on accounts once due AND payment has been demanded.
- Rate
- 9%
- Statute
- RSMo § 408.020
- Type
- Fixed by statute.
- Source
- revisor.mo.gov · verified July 9, 2026
Statute text read on revisor.mo.gov, a legal mirror, because the official Missouri site blocks automated access. Confirm it against the official code before relying on it in a dispute.
What 9% comes to on an unpaid invoice
Simple interest at 9% a year on a 365-day year. Count the days from when interest starts to run in Missouri, which is not always the due date.
| Invoice | 30 days | 60 days | 90 days |
|---|---|---|---|
| $5,000 | $36.99 | $73.97 | $110.96 |
| $10,000 | $73.97 | $147.95 | $221.92 |
| $50,000 | $369.86 | $739.73 | $1,109.59 |
Work out the interest on your invoice
Prefilled with Missouri's legal rate of 9%. If your contract sets a rate, use that instead.
Interest you can claim
$147.95
$10,147.95 with the invoice · $2.47 a day
The ceiling
How high can a late fee go in Missouri?
Your contract decides. The rate above only applies when your terms are silent. Between businesses, an agreed late-interest rate or late fee replaces it, within two limits: the state's ceiling on agreed rates, and the rule that a late fee must compensate you rather than punish the customer.
Missouri's ceiling on an agreed rate wasn't part of our verified research, so check the state's usury law, or ask a lawyer licensed in Missouri, before writing the common 1.5%-a-month (18%) rate into your terms.
Late payment wording for a Missouri invoice
On your invoice
Payment is due by the date shown on this invoice. Late payments are subject to interest at 9% a year, the legal rate under RSMo § 408.020.
This restates what Missouri law applies when your contract is silent. If your contract sets a rate, quote that instead. The wording doesn't say when interest starts, because that differs by state; the note at the top of this page covers it where Missouri law sets it.
How Missouri compares
Of the 46 states with a rate that applies on its own, 13 set a higher one and 30 a lower one. The middle of the range is 8%.
Interest is the fallback. Getting paid on time is the plan.
DueTrail turns overdue invoices into managed cases with reviewable reminders and recorded promises to pay, so invoices get settled before anyone reaches for RSMo § 408.020.