Reference · Oklahoma · 2026
Oklahoma late payment interest rate
When your contract sets no rate, the Oklahoma figure for interest on an overdue B2B invoice is 6%, under 15 O.S. § 266.
In the absence of any contract as to the rate; parties may agree to any lawful rate.
- Rate
- 6%
- Statute
- 15 O.S. § 266
- Type
- Fixed by statute.
- Source
- law.justia.com · verified July 9, 2026
Statute text read on law.justia.com, a legal mirror, because the official Oklahoma site blocks automated access. Confirm it against the official code before relying on it in a dispute.
What 6% comes to on an unpaid invoice
Simple interest at 6% a year on a 365-day year. Count the days from when interest starts to run in Oklahoma, which is not always the due date.
| Invoice | 30 days | 60 days | 90 days |
|---|---|---|---|
| $5,000 | $24.66 | $49.32 | $73.97 |
| $10,000 | $49.32 | $98.63 | $147.95 |
| $50,000 | $246.58 | $493.15 | $739.73 |
Work out the interest on your invoice
Prefilled with Oklahoma's legal rate of 6%. If your contract sets a rate, use that instead.
Interest you can claim
$98.63
$10,098.63 with the invoice · $1.64 a day
The ceiling
How high can a late fee go in Oklahoma?
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.
Oklahoma'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 Oklahoma, before writing the common 1.5%-a-month (18%) rate into your terms.
Late payment wording for a Oklahoma invoice
On your invoice
Payment is due by the date shown on this invoice. Late payments are subject to interest at 6% a year, the legal rate under 15 O.S. § 266.
This restates what Oklahoma 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 Oklahoma law sets it.
How Oklahoma compares
Of the 46 states with a rate that applies on its own, 32 set a higher one and 5 a lower one. The middle of the range is 8%.
Same 6% figure: Alabama, Arkansas, Maryland, Minnesota, North Dakota, Pennsylvania, Texas and Virginia.
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 15 O.S. § 266.