How prompt payment deadlines and interest are counted
On federal work the clock for paying an invoice is set by statute, and missing it creates an automatic interest penalty rather than something the payer has to agree to. Enter the amount invoiced, the date the payment request was received, the date of payment and the period that applies, and this tool returns the due date, the number of days late and the interest penalty.
The Prompt Payment Act at 31 U.S.C. §3903 requires an agency to pay construction progress payments within 14 days of receiving a proper payment request, and 31 U.S.C. §3905(b) requires a prime contractor to pay its subcontractors within 7 days of receiving payment from the government. Other federal invoices generally fall under the 30-day rule in 5 C.F.R. part 1315. The interest rate is the Contract Disputes Act rate that the Treasury sets every six months, so it is left blank here on purpose - look up the rate in force for your period rather than assuming one. Private and state projects follow the contract or a state prompt pay act instead. Provisions described are those in force as of September 2026. The due date is counted from the day after receipt, and days late are counted the same way from the day after the due date.
An invoice that is incomplete or disputed may not be a proper payment request, which changes the start date entirely. This calculator is for reference only and is not legal advice. Consult a licensed attorney about your specific situation.
Frequently asked questions
Treasury publishes a new Prompt Payment interest rate every January and July, so no single figure stays correct. Enter the rate in force during the late period instead of relying on a stored default.
No. Section 3905(b) applies to federal contracts. On private work the payment period comes from the subcontract or from the prompt pay statute of the state where the project sits.