Your terms, your figures
Enter the invoice amount, dates and agreed grace days, then choose a monthly percentage, a one-time flat fee or both. An optional minimum or cap applies once to the combined fee, never to the invoice principal.
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Invoice late fee calculator
Turn your agreed payment terms into a clear breakdown and a ready-to-edit reminder. This overdue invoice calculator works with your contractual monthly percentage, a flat fee, or both — in USD, AUD, EUR, GBP or CAD.
For businesses in the US, Australia and worldwide. All fee figures come from you; no legal rate is assumed.
Your late fee estimate
Late fees must be agreed in the contract or invoice terms. Limits vary by US state and by country, including usury and consumer rules. Check your local rules. This estimate does not establish a right to charge.
Your terms. A transparent breakdown.
See the fee, the remaining balance and the annual equivalent before you follow up.
Write your payment reminder
Choose a tone, add any details and edit the wording before sending. Nothing is sent for you.
Identify the clause or terms previously agreed with your customer. The letter includes these words exactly; adding a fee now does not create an agreement.
Calculate a valid estimate first to generate your letter.
Calculations and letters stay in your browser. Your draft is saved locally for up to 7 days, then removed when next checked, or cleared when you use it after signup.
How this late payment fee calculator works
Daily proration, clear periods
Monthly periods start from the due date plus grace days. Each period ends on the same day of the next month, or its last day if shorter. The monthly percentage is prorated by the actual days in that period. The due date and grace days are excluded; the calculation date is included.
Payments and compounding
Partial payments reduce principal from the following day. Fees stop accruing once principal is paid; already accrued fees remain. Simple fees use unpaid principal only. Monthly compounding adds prior percentage fees to the next period’s balance, excluding flat fees and minimum adjustments. Use it only if agreed and permitted.
Equivalent nominal APR is the monthly percentage × 12. The effective annual rate also reflects monthly compounding when selected. These comparisons exclude flat fees, minimums, caps, grace days and partial payments; they are not a regulated APR disclosure. Flat-only fees have no monthly-rate APR equivalent.
The calculation and editable reminder stay in your browser. A draft is kept in localStorage on this device for up to seven days, so you can review the invoice after signup. Nothing is stored server-side before signup.
Looking for late payment interest?
For Spain or UK statutory interest, or a custom annual rate, use our separate interest calculator.
Late payment interest calculator →Invoice late fee questions
What is the standard late fee on an invoice?
There is no single standard late fee that applies to every invoice. Use the fee agreed in your contract or accepted invoice terms, and check the rules that apply to the transaction. A rate used by another business is not proof that it is lawful or enforceable for yours.
How much can I charge for late payment of invoices?
It depends on the agreed terms and local law. Limits vary by US state and by country, and usury and consumer rules may apply. Check whether the fee, grace period, minimum, cap and any compounding were agreed and are permitted before charging. This calculator models the figures you enter; it does not validate their legality.
What late fee invoice wording can I use?
For a reminder, adapt: “Under clause [reference] of our agreed payment terms, a late fee of [amount and currency] has accrued on invoice [number] as of [date]. The unpaid invoice balance is [amount] and the total requested is [amount]. Please confirm payment or contact us to discuss any discrepancy.” Replace every placeholder and check the calculation. Adding wording to an overdue invoice does not by itself establish prior agreement to a fee.
Can I use this calculator in the US, Australia or elsewhere?
Yes. This is a contractual late fee calculator for invoices in USD, AUD, EUR, GBP or CAD. You enter your own agreed figures. Selecting a currency does not select a law, supply a legal rate or convert money. Check your contract and local rules wherever you or your customer are based.