Invoice Late Fee Percentage: What to Charge and How to Word It

The benchmark most businesses use is 1.5% per month, which equals 18% per year (APR). This is not a legal requirement — it is an industry norm that has become the de facto standard because it sits at the intersection of being high enough to incentivise timely payment and low enough that most clients will pay it without dispute.

Here is how common late fee rates compare:

Many businesses combine both: a flat administrative fee (£25–£50) plus a percentage rate. This covers the overhead of chasing regardless of invoice size.

To learn how to set up a full late fee system, see how to charge late fees on invoices.

You can express your late fee as a monthly rate or an annual rate — both are valid, but they create different impressions and have different practical uses.

Monthly rates are simpler to calculate and more intuitive for short-term late payments. If a client is 30 days late on a £2,000 invoice and your rate is 1.5% per month, the fee is a straightforward £30. No proration calculation needed.

Annual rates (APR) are required in some jurisdictions for consumer invoices and are useful when you want to make the cost of lateness feel significant. "18% per year" sounds more substantial than "1.5% per month" even though they are identical.

Best practice: state both on your invoice. "A late fee of 1.5% per month (18% per annum) will be charged on overdue balances." This covers you legally (especially important in jurisdictions that require APR disclosure) and leaves no ambiguity.

For payment terms guidance more broadly, see the freelance payment terms guide.

Late fee rules vary significantly by jurisdiction. Here is a practical summary for the most common markets:

United Kingdom

Under the Late Payment of Commercial Debts (Interest) Act 1998, B2B creditors are automatically entitled to charge 8% per annum above the Bank of England base rate on overdue commercial invoices — even without a contractual clause. You can contract for a higher rate, but it must not be "substantial remedy" — courts have struck down unconscionably high rates. You are also entitled to claim a fixed debt recovery cost (£40 for debts under £999, £70 for £1,000–£9,999, £100 for £10,000+).

United States

There is no federal late fee law for B2B invoices. State usury laws set maximum interest rates, but most states exempt commercial contracts from usury caps entirely — meaning freedom of contract applies. Practically, 1.5–2% per month is enforceable in virtually all states. For B2C invoices, usury limits are more restrictive; check your state law. Always include the rate in your written contract.

Australia

No statutory B2B late payment interest rate. Freedom of contract applies. The standard market rate of 1.5% per month is common and enforceable if stated in the contract. The Australian Consumer Law (ACL) applies to B2C transactions and can limit penalty clauses, but B2B late fees are generally not subject to these restrictions.

European Union

The Late Payment Directive (2011/7/EU) gives B2B creditors the right to charge interest at 8% above the ECB reference rate on invoices more than 30 days overdue (or 60 days if contractually agreed). EU member states must ensure creditors can at minimum recover this statutory rate. Contractual rates higher than statutory are permitted.

The formula for a monthly percentage late fee is straightforward:

Late fee = Invoice amount × (monthly rate / 30) × days overdue

Or, if you charge by full calendar month (most common for monthly billing cycles):

Late fee = Invoice amount × monthly rate × months overdue

Here is a worked example using daily proration:

Invoice amount:        £3,500.00
Due date:              1 February 2026
Payment received:      21 February 2026
Days overdue:          20 days
Late fee rate:         1.5% per month

Daily rate:            1.5% ÷ 30 = 0.05% per day
Daily fee:             £3,500 × 0.0005 = £1.75/day
Total late fee:        £1.75 × 20 days = £35.00

Amount now due:        £3,535.00

And the same invoice charged by full months (simpler, less precise):

Invoice amount:        £3,500.00
Months overdue:        1 full month
Monthly rate:          1.5%
Late fee:              £3,500 × 0.015 = £52.50

Amount now due:        £3,552.50

Use the daily proration method for client-friendly accuracy. Use the full-month method when your billing cycle is monthly and simplicity matters more than precision. To automate this calculation, use the free late fee calculator.

Vague late fee clauses get disputed. Specific wording gets paid. Here are three proven phrasings at different levels of formality:

Standard (recommended for most businesses)

Payment terms: Net 30. Payment is due by [DATE].

A late payment fee of 1.5% per month (18% per annum) will be
applied to any balance outstanding beyond the due date.
This fee compounds monthly on the unpaid balance.

With flat administrative fee

Payment due: [DATE] (Net 30).

Overdue invoices incur an administrative charge of £40 plus
interest at 1.5% per month on the outstanding balance from
the due date until the date of payment.

Short-form for smaller invoices

Due: [DATE]. Late payments subject to 1.5%/month interest.

Whichever wording you use, include it on every invoice — not just in the contract. Many clients do not re-read the contract before processing an invoice. Putting the terms on the invoice itself creates no ambiguity and removes the "I didn't know" defence.

For more on payment terms language, see the guide to avoiding late payments.

The hardest part of late fees is not the legal side — it is the relational side. Most freelancers and small business owners feel uncomfortable enforcing fees against clients they like. Here is a framework that keeps you firm without being adversarial.

1. Make it a policy, not a personal decision

When a client questions the fee, the answer is: "This is our standard late payment policy, stated in our agreement and on the invoice. We apply it consistently across all clients." This removes the personal element and makes it procedural. You are not punishing them — you are enforcing a previously agreed policy.

2. Notify before enforcing

Send a reminder the moment the invoice goes overdue — ideally the same day or next morning. Reference the late fee in that reminder so the client knows it is accruing. Sending a late fee bill 45 days later without any notice creates resentment. Notifying on day 1 creates urgency.

3. Waive strategically, not reflexively

For a valuable long-term client who is genuinely apologetic and pays promptly once reminded, waiving the fee once is a reasonable goodwill gesture — and it strengthens the relationship. But waive it every time and you have trained them that the fee has no real consequence. Track waivers per client and treat a pattern of late payment as a separate conversation about terms.

4. Escalate systematically

If the invoice remains unpaid past 60 days with fees accruing, move from reminders to formal demand — then to collections or small claims if necessary. Track every invoice and every client interaction so you have a clear timeline if you need to escalate. A structured AR process (not ad-hoc chasing) is what separates businesses that collect versus businesses that write off bad debt.

InvoiceGrid automates the reminder sequence and logs every interaction, so you always know exactly where each invoice stands. See also freelance payment terms guide for the full picture on structuring client payment agreements.