When a client pays late, you have a legal right to charge interest in most jurisdictions. Here's how to calculate it, what the rates are, and whether you should actually charge it (spoiler: usually not — automated chasing works better and preserves the relationship).
Quick reference — statutory interest rates
🇬🇧
UK
8% + Bank of England base rate
Late Payment of Commercial Debts Act 1998
🇪🇺
EU
8% + ECB reference rate
EU Late Payment Directive 2011/7/EU
🇺🇸
US
Contract-dependent
Typically 1.5%/mo if stated in contract
In this article:
The formula for calculating simple interest on an overdue invoice is:
Interest = Amount × Rate × (Days / 365)
Worked examples:
UK — £2,000 invoice, 45 days late
£2,000 × 0.08 × (45 / 365) = £19.73
Plus £40 fixed compensation for invoices under £1,000, £70 for £1K–£10K
EU — €5,000 invoice, 30 days late
€5,000 × 0.08 × (30 / 365) = €32.88
Plus €40 flat-rate recovery cost
US — $3,500 invoice, 60 days late (1.5%/mo in contract)
$3,500 × 0.18 × (60 / 365) = $103.56
1.5%/month = 18% annual rate (must be in contract)
The Late Payment of Commercial Debts (Interest) Act 1998 gives UK businesses an automatic right to charge interest on late B2B invoices — no contract clause needed.
📊 Interest rate
Bank of England base rate + 8% per year. With the base rate currently at ~5.25%, the total is approximately 13.25% per year.
💷 Fixed compensation
On top of interest:
• £40 for invoices under £1,000
• £70 for £1,000–£9,999
• £100 for £10,000+
💡 Tip:For consumer clients (B2C), the Late Payment Act does NOT apply — you'd need to rely on contract terms instead. The Act covers B2B transactions only.
The EU Late Payment Directive 2011/7/EU applies across all EU member states. It gives creditors the right to claim interest automatically when a B2B invoice goes unpaid.
Individual countries may have slightly different implementations. The Netherlands (relevant for ZZP freelancers) applies the same rates via BW art. 6:119a. See also: Late Payment Fees Guide.
Unlike the UK and EU, the US has no federal statutory right to charge late payment interest on commercial invoices. Each state has its own rules, and most require the rate to be stated explicitly in your contract or on your invoice.
Common US practice:
Recommended invoice language (US):“Invoices unpaid after [30/14] days are subject to a late fee of 1.5% per month (18% annually) on the outstanding balance.”
Best practice: state your late payment policy on every invoice. Copy-paste for each jurisdiction:
🇬🇧 UK
Late payments are subject to statutory interest under the Late Payment of Commercial Debts Act 1998 (8% above the Bank of England base rate) plus fixed compensation.
🇪🇺 EU
Bij te late betaling is de wettelijke handelsrente verschuldigd (BW art. 6:119a) en een incassokosten van €40.
🇺🇸 US
Invoices unpaid after 30 days will incur a late fee of 1.5% per month (18% per annum) on the outstanding balance.
You have the right to. But exercising it is a different question.
✅ Charge it when:
⚠️ Skip it when:
🐕 The Chaser approach:
In practice, most overdue invoices don't need interest charges to get paid. They need professional, escalating follow-up. Chaser's 4-stage sequence (day 3, 7, 14, 30) resolves the vast majority of late payments — without damaging client relationships or getting into legal territory. Save interest charges for the genuinely difficult cases.
Try automated follow-up first → free for 3 invoicesWhat is the legal interest rate for overdue invoices in the UK?
In the UK, the statutory interest rate for late commercial payments is 8% per year plus the Bank of England base rate (currently making it around 12–13% annually). This is set by the Late Payment of Commercial Debts (Interest) Act 1998. You can also claim fixed compensation of £40–£100 depending on the invoice size.
Can I charge interest on overdue invoices without mentioning it in my contract?
In the UK and EU, yes — the statutory right to charge interest on B2B invoices exists by law. You don't need to mention it in the contract. However, it's best practice to state it on your invoices or in your terms to avoid disputes. In the US, you generally need to have it in the contract.
How do I calculate interest on a late invoice?
Formula: Interest = Invoice Amount × Annual Rate × (Days Overdue / 365). Example: £2,000 invoice, 8% annual rate, 45 days late = £2,000 × 0.08 × (45/365) = £19.73. Add any fixed compensation on top of this.
Should I actually charge interest on late invoices?
It depends. For one-off clients or large disputed amounts, yes. For long-term clients with a good track record, a professional escalating email sequence (automated by Chaser) tends to work better and preserve the relationship. Most freelancers never need to actually charge interest — consistent follow-up gets the invoice paid first.
They need professional follow-up. Chaser sends the right email at the right time, automatically. Free for 3 invoices — no credit card.
Start free →See also: Late payment fees guide