Guides · Free tool

Invoice Late Fee Calculator

By Marissa · Founder of Dunn · Freelancer for 15+ years · Updated October 28, 2026

Work out what a late invoice owes you today, what it adds up to if it stays unpaid, and copy the exact words for your invoice and contract. Free, no sign-up, nothing saved.

Your wording, ready to copy

Filled in with the numbers above. Add names to personalize the emails (optional, never saved):

How the late fee is calculated

Every method charges only the original invoice amount: never a fee on a fee. Nothing is charged until the grace period ends.

• Flat fee: the flat amount, once, the day after the grace period ends. $25 on any invoice.
• Percent, one time: invoice × percent. 5% of $2,000 = $100.
• Percent a month, charged by the day: invoice × monthly rate ÷ 30 × days late after the grace period. $2,000 × 1.5% ÷ 30 × 45 days = $45.
• Flat + monthly: the flat fee once, plus the monthly charge. $25 + $45 = $70 at 45 days late.
• Cap: if you set one, the late charges stop growing once they reach it.

What works for different businesses

• House and office cleaners: a small flat fee ($10–25) beats a percent. 1.5% of a $150 clean is $2.25, which changes nothing.
• Photographers: keep the fee in proportion to the package. Clients push back hard on a fee that's a big share of the bill, and many photographers rely on delivering the gallery after payment instead.
• Contractors, plumbers, electricians: 1.5% a month on balances past net 30 is the long-standing norm for commercial work. Billing homeowners usually means stricter rules.
• Designers, agencies, consultants: a monthly percent with a short grace period, written into the contract, and a friendly reminder before the fee lands keeps big clients on side.

Before you charge a late fee

• Agree on it first. Put it in your contract or quote and on every invoice. A fee added after the work is done is hard to enforce.
• Keep it in proportion. A fee that's out of proportion to the invoice can be thrown out as a penalty.
• Apply it to everyone, and decide in advance when you'll waive it (a first-time slip, a real hardship).
• Remind before it lands. A friendly note before the due date catches most "forgot" cases, so you rarely need the fee at all.

A few US rules worth knowing

Last checked October 28, 2026. This is general information, not legal advice. Rules vary by state, and they are stricter when you bill individuals for personal or household services than when you bill businesses.

• Freelancer pay laws. If your contract has no payment date, these laws generally say clients must pay within 30 days of the work being done: New York City (contracts of $800+), New York State ($800+), California ($250+), Los Angeles ($600+ a year), Illinois ($500+) and Seattle ($600+ a year).
• When no rate was agreed, states set a default interest rate on unpaid contract debts, usually applied by a court. Examples: California 10%, New York 9% (2% on consumer debts owed by individuals), Colorado 8% a year.
• 1.5% a month is a business convention, not a national rule. Georgia, for example, writes it into law for commercial accounts 30 or more days overdue.

Read more: How to charge a late fee on an invoice · What to say when a client pays late · Invoice reminder email templates

Quick answers

How much late fee should I charge on an invoice?
Commonly cited ranges are a flat $25 to $50, or about 1% to 1.5% of the invoice per month. Keep it in proportion to the invoice: a flat $50 is fine on a $3,000 project but heavy on a $150 cleaning.

How do I calculate a late fee?
For a monthly rate charged by the day: invoice amount × monthly rate ÷ 30 × days late after the grace period. A $2,000 invoice at 1.5% a month, 45 days late, is $2,000 × 0.015 ÷ 30 × 45 = $45. A flat fee is simply the flat amount once the grace period ends.

Can I charge a late fee if it wasn't in my contract?
Generally no. A late fee is usually only enforceable if your client agreed to it before the work started, in a contract, quote or your terms. For existing clients, announce the fee in writing and apply it only to invoices sent after the date you give.

Is a 1.5% monthly late fee legal?
1.5% a month (18% a year) is a long-standing business convention, and Georgia's law allows up to 1.5% a month on commercial accounts 30 or more days overdue. But states set different limits, and the rules are stricter when you bill individuals for personal or household services. Check your state's rules. This is not legal advice.

Should I charge a flat fee or a percent?
A flat fee is simple and works best for small, frequent invoices like cleaning. A percent per month scales with the invoice and suits larger projects. Some businesses use both: a flat fee once, then a monthly percent if it stays unpaid.

Does the late fee start on the due date?
It starts whenever your terms say. With no grace period, the fee applies the day after the due date. With a 7-day grace period, the first fee applies on the eighth day after the due date.

Can I charge interest on a late fee?
It's safest not to. Charge late fees on the original invoice amount only (simple, not compounding), unless your signed contract clearly says otherwise. Some states restrict charging fees on fees.

How do I tell an existing client I'm adding a late fee?
Give a few weeks' notice in writing, apply it only to invoices sent after a set date, and apply it to every client. This calculator writes the announcement email for you with your numbers.