Late Payment Fees on Invoices: Clause Wording, Rates and Legal Limits

You can charge a late fee on an invoice when your contract or invoice terms say so and the rate is allowed where you and your client work. In the UK and the EU, a business can also claim statutory interest and a fixed recovery cost without any clause. This guide gives the official UK and EU rules, example clause wording and a worked calculation. It gives no US rate, because your state and your contract decide that.

A fee clause you cannot enforce is worse than none: it signals rules you will not apply. Get the wording and process right before the first overdue invoice.

Legality basics by region

Whether a fee is allowed depends on your contract and the law where you and your client are. The UK and EU rules below come from the official pages named in each point. Consumer and public-sector contracts can carry stricter rules, so check them before you add a fee.

• United States: this guide gives no US legal rate. Rules on late fees and interest are set by each state, and your industry may have its own. Check your state's rules before you add a clause.
• European Union: Directive 2011/7/EU sets statutory interest for late payment at the European Central Bank reference rate plus at least 8 percentage points (Article 2(6)). Public authorities pay within 30 days, or in very exceptional cases 60. Businesses pay within 60 days unless they expressly agree otherwise, and the agreed term must not be grossly unfair. EU countries may keep rules more favourable to creditors.
• United Kingdom: statutory interest on late business-to-business payments is 8% plus the Bank of England base rate, and you cannot claim it if the contract sets a different rate. You can also claim fixed compensation for recovery costs: £40 for debts up to £999.99, £70 for £1,000 to £9,999.99, and £100 for £10,000 or more. Check the current base rate on GOV.UK.

Late fee structures you can use

A flat monthly percentage is simple to calculate and explain: 1.5% a month is 18% a year (1.5 × 12, simple interest). The rate is your choice, within local law. The EU and UK statutory rates move with their reference rates (the ECB rate plus at least 8 points, and the Bank of England base rate plus 8%), so a fixed monthly rate can sit above or below them.

Worked example: calculating a late fee

Invoice 2026-014 for $4,200 was due July 15. On August 29 it is 45 days overdue. Your terms say 1.5% per month on unpaid principal, simple interest (not compounded daily unless your contract says so). One month of fee: 1.5% × $4,200 = $63. If you assess monthly and another full month passes unpaid, add another $63 on the still-unpaid principal. Do not apply the percentage to the fee itself unless compounding is explicit. If the client paid $1,000 on August 10, calculate the next fee on the remaining $3,200 only. Put the math on the fee invoice so AP can verify it in under a minute.

How to word the clause on your invoice

Place terms near the total and in your master service agreement. Use plain language. Accounts payable scans for due date and penalty line.

The late-fee invoice adjustment process

• Confirm the original invoice is past due per your stated terms, not your informal expectation.
• Calculate fee on unpaid principal only (not on tax if tax was remitted separately; follow your accountant's guidance).
• Issue a separate line or supplemental invoice: "Late fee for Invoice 2026-014, 45 days overdue, 1.5% × $4,200 = $63.00."
• Reference the original invoice number and due date on every fee document.
• Send with the same payment instructions; do not assume automatic card retry covers fees.
• Record the fee in your books the way your accountant advises.

Fee-notice email template

Notify before or when you assess the fee. Tone is factual, not punitive. You want payment, not a dispute.

Subject: Invoice [2026-014] overdue: late fee applied per terms

Hi [Client First Name],

Invoice [2026-014] for [$4,200.00] was due on [July 15, 2026]. Our records show the balance remains unpaid.

Per the payment terms on the invoice, a late fee of [1.5% per month] applies to overdue balances. I have added a late fee of [$63.00] (invoice [2026-014-LF]).

Updated amount due: [$4,263.00], payable via [payment link / ACH details].

If payment is already in process, reply with the transfer date and I will waive the fee. If there is a dispute on the original invoice, let me know within 5 business days so we can resolve it before additional fees accrue.

Thank you,
[Your Name]

When not to charge a late fee

• Terms were never disclosed on the contract or invoice. You cannot invent penalties after the fact.
• The client disputed the work in writing before the due date; resolve the dispute first.
• You caused the delay (late delivery, wrong PO, missing W-9 they requested twice).
• The relationship is strategic and a fee would cost more in future revenue than the fee collects. Waive once, document it, tighten terms next contract.
• Local law caps or bans your rate (some consumer debts, government subcontractors).
• First-time slip by a reliable client. A reminder without a fee often restores the pattern.

Pair fees with prevention

Fees recover a little cost; they do not fix cash flow. Send invoices the day work is approved, require deposits on new clients, and use payment links so AP has one click. Track days-sales-outstanding in your billing tool. If average collection exceeds your terms by 10+ days, fix process before raising penalty rates.