Free Late Payment Fee Calculator
Calculate how much a client owes on an overdue invoice. Pick pro-rated annual interest (B2B commercial debt standard) or a flat late fee plus a percentage surcharge. Instant totals.
UK Late Payment Act: BoE base + 8%. US: typically 1-2% per month (~12-24% APR). EU B2B: ECB + 8%.
How the late fee calculator works
Two standard models — use whichever is in your contract or local law.
Pick interest or flat fee
Interest: daily pro-rata at an annual rate (standard in UK, EU, and most B2B contracts). Flat fee: a one-time charge, optionally plus a percentage (common in US consumer contracts).
Enter invoice details
Invoice amount, due date, and the calculation date. Leave the calculation date as today to see the current balance; set a future date to project the total if the client pays later.
Send the updated total
Use the result in a reminder email or statement of account. KipBill Pro can automate overdue reminders — no chasing required.
Why use this calculator
Instant results
Every change recalculates live — no loading, no wait. Run scenarios in seconds.
Runs in your browser
Nothing is sent to our servers. Your numbers stay on your device.
12 languages
Use it in English, Spanish, French, German, Portuguese, Italian, Dutch, Polish, Japanese, Korean, Chinese, or Arabic.
Accurate and transparent
Clean math with clear breakdowns so you understand every figure — not a black box.
Want to go further than a calculator?
Create a free KipBill account to invoice clients, track payments, manage taxes, and send reminders automatically.
Open free accountLate Payment Fee Calculator — FAQ
What late fee can I legally charge?+
It depends on jurisdiction. UK: under the Late Payment of Commercial Debts Act 1998, statutory interest is Bank of England base + 8% on B2B invoices, plus compensation (£40/£70/£100 by value). EU B2B: similar, ECB + at least 8% under Directive 2011/7. US: check your state's usury limits — typically 1-2% per month is common and legal in most states.
Does the client have to agree to late fees?+
Late fees specified in your contract or invoice terms are enforceable if the client accepted them. Statutory interest (UK Late Payment Act, EU Directive 2011/7) applies automatically to B2B debts even without a clause — you don't need permission to add it.
How is interest calculated daily?+
Annual rate ÷ 365 × days late × invoice amount. For a £1,000 invoice, 8% annual rate, 30 days late: 0.08 / 365 × 30 × 1000 = £6.58 interest. This calculator does it automatically.
Can I compound the interest monthly?+
UK and EU statutory interest is simple (not compound). US contracts vary — check your clause. This calculator uses simple interest by default, which is the standard for commercial debt.
Should I chase payment myself or go to court?+
Start with a polite reminder at 7 days overdue, a firm reminder at 14, and a final demand at 30 stating the interest accrued. Small claims court is usually the next step for amounts under €5,000 / £10,000 / $10,000. Most clients pay before it gets that far.
Can KipBill automate late fees and reminders?+
Yes — the Starter plan and above sends scheduled payment reminders automatically based on your chosen timeline (e.g. 7, 14, 30 days overdue) and flags overdue invoices on your dashboard.