Work out the late fee on an overdue invoice and the new total in seconds. Choose a monthly percentage, a flat fee or both, then copy a ready-made line for your payment reminder.
For US freelancers and small businesses · updated October 2026
Simple interest, 30-day months. Only charge a late fee your contract allows and your state permits.
Enter the invoice amount and how many days it’s overdue.
Choose your late fee type: a monthly percentage, a flat fee or both.
Add your rate or fee, using the same terms as in your contract.
Copy the ready-made line and paste it into your payment reminder or updated invoice.
A late fee is an extra charge for paying after the due date. Most freelancers and small businesses use one of these:
A monthly percentage: interest that keeps adding up while the invoice stays unpaid, such as 1.5% a month.
A flat fee: a fixed amount, such as $25, added once the invoice is late.
Both: a flat fee when the invoice becomes late, plus monthly interest after that.
Late fee = invoice amount × monthly rate × days overdue ÷ 30
For example, a $5,000 invoice with a 1.5% monthly late fee that’s paid 45 days late picks up $112.50. If it’s paid 30 days late, the fee is $75. Add a $25 flat fee and the 45-day late fee comes to $137.50.
A monthly rate sounds small, but it adds up over a year. Here’s what common monthly late fees work out to:
Monthly late fee
Per year
1%
12%
1.5%
18%
2%
24%
This calculator uses simple interest, where the fee is charged on the original invoice amount only. It’s what most freelancers use and the easiest for clients to check.
Yes, as long as you set them up the right way. There’s no single federal rule for late fees on invoices; each state has its own laws, and many cap how much interest you can charge. Courts can also refuse a fee that looks like a penalty rather than a fair charge for paying late.
The safest approach is to agree on the late fee before any work starts. Put it in your contract and repeat it in the payment terms on every invoice. A fee the client never agreed to is hard to enforce.
Rules are often stricter when your clients are individuals rather than businesses, so check your state’s limits before you settle on a number.
Keep it reasonable. 1% to 1.5% a month, or a flat $25 to $50 on smaller invoices, is enough to encourage payment without looking punitive.
Match it to the invoice size. A flat fee works for small invoices; a monthly percentage scales better for large ones.
Consider a short grace period of a few days if you want to go easy on clients who pay a little late.
Be consistent. Use the same terms for every client, and send a reminder before you add the fee.
Spell out your late fee in your contract and in the payment terms on every invoice. For example:
Payment is due within 30 days of the invoice date. Overdue balances accrue interest of 1.5% per month (18% per year) from the due date until paid, plus a one-time late fee of $25.
Not sure what else your payment terms should cover? Our guide to late invoicing rules walks through the basics.
Send a polite reminder just before the due date and again shortly after it. If the invoice is still unpaid, send an updated invoice with the late fee as a separate line, and use the text from the calculator to explain it. For wording ideas, see how to remind someone to pay you and our friendly reminder email examples. Letting clients pay by card makes late payments less likely; see what it costs with our Stripe fee calculator.
Many clients pay the original amount as soon as they see the late fee, and it’s up to you whether to waive it. Waiving it once can be a goodwill gesture, but make it clear the terms still apply next time.
How do I calculate a late fee on an invoice?
What is a typical late fee for invoices?
Is 1.5% a month a legal late fee?
Can I charge a late fee if it wasn’t in my contract?
Should I charge a flat fee or a percentage?
When should I start charging a late fee?
Is there a maximum late fee I can charge?
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