Calculate UK Statutory Late Payment Interest Online Free
🚀 Calculate What You're Owed
Enter the invoice details below — the interest, compensation, and total update live. Nothing leaves your device.
🧾 Invoice Details
👤 Creditor & Debtor
📊 Statutory Rate
🧮 Calculation
📝 Letter Options
Quick answer: Enter the overdue invoice amount, the invoice/supply date, and the agreed payment due date (or flag that none was agreed, and the tool applies the default 30-day term). The tool calculates the days overdue, statutory interest at the Bank of England base rate + 8% as simple daily interest, and the correct fixed compensation tier — £40, £70, or £100 by debt size. Add your and the debtor's details, then click Download PDF for a formal demand letter citing the Late Payment of Commercial Debts (Interest) Act 1998. Everything runs locally in your browser with jsPDF — not a screenshot image. This applies to business-to-business debts only, is a calculation aid, and is not legal advice.
- Cost: Free, unlimited calculations and letters, no signup.
- Where it runs: 100% in your browser — no upload, no server storage.
- Correct statutory formula: BoE base rate + 8%, simple daily interest from day after due date.
- Correct compensation tiers: £40 (under £1,000), £70 (£1,000–£9,999.99), £100 (£10,000+).
- Default 30-day term: Applied automatically when no payment date was agreed.
- B2B only: This right does not apply to consumer debts.
⚖️ Calculation Aid, Not Legal Advice: This tool applies the standard statutory formula. Contractual terms, disputed debts, or insolvency situations can change what's actually recoverable.
📊 Check the Base Rate: The Bank of England base rate changes periodically — confirm the figure that applied during your overdue period before relying on this calculation.
🏢 B2B Debts Only: The Late Payment of Commercial Debts (Interest) Act 1998 does not apply to consumer debts.
✅ Privacy: Your invoice and debtor details are processed locally — never uploaded, transmitted, or stored anywhere.
✅ 100% Private: Your calculation and letter are generated locally in your browser using JavaScript. No data is ever uploaded to a server or stored anywhere.
Note: Your data will be cleared once you close or refresh the page, so download your PDF before leaving.
How to Calculate UK Statutory Late Payment Interest
Enter the Invoice Details
Amount, invoice date, and the agreed payment date if any.
Enter Creditor & Debtor
Add your business and the business that owes you.
Check the Base Rate
Confirm or edit the Bank of England base rate.
Download the Letter PDF
Review the calculation, then save your demand letter.
🔒 Your Invoice Details Never Leave Your Device
This tool calculates interest and builds the letter using jsPDF running inside your browser tab. There is no upload step, no server-side processing, and no network request containing your invoice amount or debtor's details.
Who Uses This Late Payment Interest Calculator?
Small Business Owners
Work out exactly what's owed on a late B2B invoice before chasing payment.
Freelancers & Contractors
Charge statutory interest and compensation on overdue client invoices.
Bookkeepers & Accountants
Produce an accurate interest calculation to support a client's credit control.
Suppliers & Wholesalers
Formalize a demand for payment on a significantly overdue trade account.
Credit Control Teams
Standardize late payment demand letters across multiple overdue accounts.
Sole Traders
Exercise the same statutory rights available to any business, large or small.
Why Use This Late Payment Interest Calculator?
- Fully Client-Side: jsPDF builds the whole letter in your browser — no upload.
- Real Vector Text: Sharp, small-file-size PDF output — not a flattened screenshot.
- Side-by-Side Preview: Check your calculation and letter next to the form as you build it.
- Correct Statutory Formula: Simple daily interest at base rate + 8%, not a rough estimate.
- Correct Compensation Tiers: £40/£70/£100 applied automatically by debt size.
- Default Term Handling: Applies the statutory 30-day default when no term was agreed.
- Editable Base Rate: Reflects the rate in force for your specific overdue period.
- 100% Free & Private: No account, no watermark, no server storing your data.
UK Late Payment Interest Calculator – Complete Guide
An overdue invoice isn't just an inconvenience - UK law gives businesses an automatic, no-questions-asked right to charge interest and a fixed fee on top, whether or not the contract mentions it. Most businesses simply don't claim it, often because working out the exact figure feels more complicated than it actually is.
The Late Payment of Commercial Debts (Interest) Act 1998, in Brief
| Element | Rule |
|---|---|
| Statutory interest rate | Bank of England base rate + 8% per year, simple interest |
| Interest starts | The day after the agreed payment date (or the default 30-day term) |
| Default payment term | 30 days after invoice date or supply of goods/services, whichever is later, if none agreed |
| Fixed compensation | £40 / £70 / £100 depending on debt size, per invoice |
| Applies to | Business-to-business debts only, including sole traders and public authorities |
Fixed Compensation Tiers
| Debt Amount | Fixed Compensation |
|---|---|
| Under £1,000 | £40 |
| £1,000 to £9,999.99 | £70 |
| £10,000 or more | £100 |
Figures reflect commonly reported 2026 guidance on the Act. The Bank of England base rate changes periodically - always confirm the rate in force for your specific overdue period before relying on a calculation.
How This Calculator Actually Works
As you enter the invoice amount, invoice date, and either an agreed due date or the "no term agreed" flag, the tool determines the correct start date for interest - using the statutory 30-day default when necessary - and counts the number of days between that date and your chosen calculation date. It multiplies the invoice amount by the daily statutory rate (base rate plus 8%, divided by 365) and that day count to get simple daily interest, then separately looks up the correct fixed compensation tier based on the debt size. Both figures, plus the original debt, are added together for the total currently claimable. On download, jsPDF draws the demand letter as genuine vector text, with the full calculation breakdown included so the debtor can see exactly how the figure was reached. Nothing ever touches a server.
Security and Privacy Considerations
- No Data Upload: Every field you fill in stays on your device.
- No Server Processing: Calculation and PDF generation run entirely as client-side JavaScript.
- No Storage: Nothing about your invoice or letter is saved once you close or refresh the tab.
- No Account Needed: There is no login, tracking, or usage cap.
Browser Compatibility and Technical Requirements
This UK Late Payment Interest Calculator works in modern browsers that support JavaScript PDF generation (jsPDF) and Blob downloads.
- ✅ Chrome/Edge 76+
- ✅ Firefox 55+
- ✅ Safari 13.1+
- ✅ Mobile Chrome (Android), Mobile Safari (iOS) — download supported
Troubleshooting Common Issues
Explanation: Interest only starts accruing from the day after the due date, not the due date itself, and the calculation runs through to your chosen "calculate as of" date. Solution: Double-check the due date and calculation date are both correct, and remember a debt due "today" shows zero days overdue until tomorrow.
Explanation: The correct rate is the one in force when the debt became overdue, which may differ from today's rate if time has passed. Solution: Check the Bank of England's published rate history for the relevant date before finalizing your figure.
Explanation: The PDF needs both parties identified to be a meaningful letter. Solution: Fill in both your business name and the debtor's business name, then download again.
Explanation: The Late Payment of Commercial Debts (Interest) Act 1998 only covers business-to-business debts. Solution: This tool isn't appropriate for consumer debts - consumer late fees are governed by different, more limited rules.
Frequently Asked Technical Questions
Question 1: What actually builds the PDF - is it a known library?
Answer: This tool uses jsPDF, a widely used open-source JavaScript library for generating PDF documents in the browser, loaded directly in your browser tab.
Question 2: What's the exact interest formula used?
Answer: Interest = Invoice Amount \u00d7 ((Base Rate + 8) \u00f7 100) \u00f7 365 \u00d7 Days Overdue - simple daily interest at the statutory annual rate, with no compounding.
Question 3: How is the default 30-day due date calculated?
Answer: When no agreed term is flagged, the tool adds 30 days directly to the invoice/supply date you've entered, matching the Act's default rule for when no payment term was contractually agreed.
Question 4: How is the fixed compensation tier selected?
Answer: The tool compares the invoice amount against the \u00a31,000 and \u00a310,000 thresholds and selects \u00a340, \u00a370, or \u00a3100 accordingly, adding that fixed figure once per invoice regardless of how overdue it is.
Question 5: Does this tool need an account, server, or API key?
Answer: No. jsPDF and the live preview both run as ordinary JavaScript already loaded by this page — you never need an account or any API key to use it.
Glossary of Terms
- Statutory Interest
- Interest a creditor is automatically entitled to charge on an overdue B2B debt under the Late Payment of Commercial Debts (Interest) Act 1998, at the Bank of England base rate plus 8% per year.
- Bank of England Base Rate
- The Bank of England's official interest rate, published periodically, which forms the base figure for UK statutory late payment interest.
- Fixed Compensation
- A one-off sum (£40, £70, or £100 depending on debt size) a creditor can claim per overdue invoice under the Act, separate from interest.
- Substantial Remedy
- A contractual alternative to the statutory right that must be fair and adequate to override it; an inadequate contractual term does not displace the statutory right.
- B2B Debt
- A debt arising from a commercial contract between businesses (including sole traders acting commercially and public authorities), as distinct from a consumer debt.
Frequently Asked Questions
Yes, completely free with no watermark, no signup, and no limit on how many calculations or letters you create.
No. The calculation and letter are built entirely inside your browser using JavaScript. Nothing is transmitted over the network.
Under the Late Payment of Commercial Debts (Interest) Act 1998, you can charge statutory interest at the Bank of England base rate plus 8 percentage points per year, calculated as simple interest from the day after the payment became due until it's paid.
This changes periodically - this tool pre-fills a recent published figure but always lets you edit it, since the correct rate is the one in force when the debt became overdue. Check the current and historic rate at bankofengland.co.uk before relying on a calculation.
£40 for debts under £1,000, £70 for debts from £1,000 to £9,999.99, and £100 for debts of £10,000 or more - a separate, one-off amount per invoice, on top of statutory interest.
No. The Late Payment of Commercial Debts (Interest) Act 1998 only applies to business-to-business transactions, including sole traders acting in the course of business and public authorities - not to consumer debts.
From the day after the agreed payment date. If no payment date was agreed in the contract, the default under the Act is 30 days after the later of the invoice date or the date the goods or services were supplied.
A contract can specify a different remedy for late payment, but only if it provides a "substantial remedy" for the late payment - otherwise the statutory right under the Act continues to apply regardless of what the contract says.
Yes - the EU Late Payment Directive (2011/7/EU) gives a broadly similar right to statutory interest and a minimum €40 fixed compensation on B2B debts, but the reference interest rate is set by each member state's central bank rather than the Bank of England, so this UK-specific calculator doesn't cover EU rates.
No. It formally asserts your statutory entitlement and puts the debtor on notice, which can prompt payment or strengthen a later court claim, but it has no independent enforcement power by itself.
Final Thoughts
Most UK businesses are entitled to statutory interest and compensation on overdue invoices and simply never claim it. This tool does the calculation correctly - the right rate, the right start date, the right compensation tier - and turns it into a clear, properly cited demand letter, all without your invoice or debtor's details ever leaving your device.
Enter your overdue invoice details above and download your demand letter!