How to Charge Late Fees on Overdue Invoices

Picture this: a client is three weeks past due and you want to add a late fee to the chaser you're about to send. You check your invoice. There's no mention of a late fee anywhere. Now you're stuck — because a charge you introduce after the fact is very hard to enforce, and bringing it up at this point just looks like improvised pressure.

That's the scenario this guide is designed to prevent. State your late-fee policy in the contract and on every invoice before there's ever a dispute, and the fee becomes a term the client agreed to rather than a surprise penalty.

Can You Charge a Late Fee?

Yes, provided the client agreed to it (or the law gives you the right regardless). The real work happens up front: put the policy in writing before work starts, and you're on firm ground. Leave it out entirely, and enforcement gets complicated.

How Much Is Reasonable?

Late fees usually take one of two forms: a flat fee per overdue invoice (for example, £25 or $35) or a percentage of the outstanding balance charged monthly. The most commonly used rates are 1% to 1.5% per month on the overdue balance, which is the same idea as monthly interest.

Keep it proportionate. A fee that looks punitive rather than compensatory can be challenged, and an aggressive rate damages the client relationship more than it's worth. It's also worth avoiding stacking a large flat fee and a high monthly percentage on the same small invoice — pick one primary mechanism and keep the rate sensible.

The Rules Differ by Country

General guidance, not legal advice. Late-fee and interest rules vary by country and change over time. The figures below are illustrative — agree your fee in writing in advance and confirm the current statutory rates and caps with your local authority or a professional before relying on them.

United Kingdom: for qualifying business-to-business debts, the Late Payment of Commercial Debts legislation gives a statutory right to interest at 8 percentage points above the Bank of England base rate, plus fixed compensation (£40, £70, or £100 depending on the size of the debt), even if your contract is silent. It does not apply to consumer debts. You can set your own contractual rate instead, but it must be a substantial remedy for late payment, otherwise statutory interest can still apply.

United States: there's no single federal rule. Enforceability and caps are mainly matters of state law, and the rules can differ between contractual interest, late fees, consumer debts, and commercial accounts. A late fee is generally enforceable if it was agreed in advance and stays within your state's limits.

Canada and Australia: charging interest on overdue accounts is common and generally enforceable when it's a written, agreed term. In Australia, the usual approach is to state a contractual rate on your invoice. In Canada, if you express interest monthly (for example 1.5% per month), also state the equivalent annual rate in writing. Under the Interest Act, interest above 5% per year may otherwise be unrecoverable.

Bottom line: agreeing the fee in writing in advance is what makes it stick almost everywhere. For the exact statutory rates and caps that apply to you, check your local government or tax authority, as the figures change.

How to Word Your Late-Fee Policy

Put the policy where the client can't miss it: in the contract and as a line near the payment terms on every invoice. Keep it specific — state when the fee starts, how it's calculated, and how often it recurs.

Example wording:

Payment is due within 30 days of the invoice date. Overdue balances are subject to a late fee of 1.5% per month (or the maximum permitted by law, if lower), applied from the first day after the due date.

The phrase "or the maximum permitted by law, if lower" is a useful safety net: it keeps your clause valid even in a jurisdiction that caps the rate below what you wrote.

One common question is whether you can charge a late fee if it wasn't in your contract. It's much harder to enforce a fee you introduce after the invoice is already overdue. The exception is jurisdictions with statutory late-payment rights, notably UK B2B invoices, where interest and compensation can apply even if your contract is silent. Everywhere else, state the policy in writing before the work starts.

Charging the Fee Without Burning the Bridge

A late fee is leverage, not a first move. The goal is to get paid and keep the client, so escalate gently.

Start with a friendly reminder a few days before the due date, then a clear note on the day it's overdue. If it stays unpaid, send a follow-up that references your agreed late-fee terms — often the mention alone prompts payment. Only apply the fee when the invoice is significantly overdue, tell the client you're doing it, and explain how it was calculated. Charging from the first day past due, as stated in your terms, is standard practice; charging it as a surprise weeks later is not.

Our guide on getting invoices paid faster covers the reminder cadence in detail. Clear payment terms prevent most late payments before they start.

Add It to Your Invoice in Seconds

You can add a late-fee line to the notes or terms section of any template using our free invoice generator. Set your payment terms, drop in the wording above, and download a clean PDF. Browse the industry templates if you want a pre-filled starting point for your trade.

Want to know what an overdue invoice has already cost in interest? Our late payment interest calculator works it out from the amount, days late, and rate.