Figure the late fee on an overdue invoice. Enter the invoice amount, your monthly late fee rate, and how many months overdue — and see the fee and the new total owed.
A simple (non-compounding) monthly late fee. Late fees are regulated — many states cap the rate and require the fee to be stated in your contract. Confirm what's allowed where you operate.
Multiply the invoice amount by your monthly late-fee rate, then by the number of months overdue. A $1,000 invoice at 1.5% per month, two months late, is a $30 fee — $1,030 owed.
Late fee = invoice × monthly rate × months overdue
Late fees must be disclosed in your terms and can't exceed state limits, so set a rate you can actually enforce.
A late fee is a charge you levy on a customer for holding your money past the date they agreed to pay it. It is not interest in the lending sense and it is not a penalty a court hands down — it is a term of the contract you and the customer entered into, which is the single most important fact about it. If the fee was not in the quote, the contract or the invoice terms before the work started, adding it after the invoice goes unpaid is a request, not a right, and a customer who declines to pay it is usually on solid ground. Everything else on this page assumes the fee was disclosed up front.
The calculator loads with a $1,000 invoice, a 1.5% monthly rate and two months overdue. The arithmetic is one line: $1,000 × 0.015 × 2 = $30. The new total owed is $1,000 + $30 = $1,030, and the "roughly per day" figure divides the fee across the elapsed period at thirty days to the month — $30 ÷ 60 = $0.50 a day. That per-day number is the one worth quoting in a chase email, because $0.50 a day is a sentence a customer understands and "1.5% per month" is not.
The fee here is simple, not compounding: each month adds another 1.5% of the original $1,000, so six months overdue is $90 and twelve months is $180 — 18% of the balance across a year. Some firms instead charge 1.5% on the running balance including fees already added, which compounds to 19.56% over twelve months, or $195.60 on the same invoice. The $15.60 difference is small on one invoice and is not small across a year of them, so know which method your terms describe. This calculator does the simple version, which is the more common and the easier to defend.
Terms of 1%–2% per month are the common range in freelance and small-business contracts, and a flat fee (say $25 per late invoice) is the usual alternative for small balances where a percentage would be trivial. Which is allowed, and how high the percentage may go, genuinely varies: many states cap what may be charged on an overdue balance, the caps often differ for consumer and commercial debt, and a rate above the cap can render the fee unenforceable rather than merely reduced. That is a question for your state's statutes or an hour of a local attorney's time — not for a calculator, and not for a number you copied from another freelancer's contract template.
This page prices one overdue invoice at one moment. The thing that actually shrinks your receivables is knowing, on any given morning, which invoices are out, how old each one is and who was chased last — which is a register, not a calculation. Our client tracker and CRM keeps every quote, invoice and due date in one pipeline with the ageing worked out for you. For the invoice itself, the invoice calculator handles discount-then-tax ordering, and how to invoice as a freelancer covers the terms that stop invoices going late in the first place.
Commonly 1–2% of the invoice per month (or a small flat fee), but many states cap the maximum. Always state the fee in your contract or invoice terms before you charge it.
Multiply the balance by your monthly percentage and by the months overdue. This tool does it and shows the new total owed.
Related: invoice calculator · freelance rate calculator · how to invoice as a freelancer.
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Yes. The Late Fee Calculator is completely free, runs in your browser, and never asks for a signup, email, or download. Enter your numbers and the result updates instantly.
It uses standard formulas and recalculates the moment you change a value, so the math is exact for the inputs you enter. Treat the result as a reliable planning estimate; for decisions with legal or tax consequences, confirm the figures with a qualified professional.
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Last reviewed: September 2026. Free to use, no signup — Late Fee Calculator by ToolWise Digital.
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