Know exactly what's owed, to the day - wherever you're based
Calculates interest and compensation owed on an overdue B2B invoice, with region presets for the UK, Ireland/EU, Australia, US, Canada and New Zealand, plus a fully custom mode for anywhere else - a single stacked bar shows principal, interest and compensation at a glance. Save every overdue invoice to a running register that totals what you're owed across all of them, any mix of regions.
The Calculator tab working out an overdue UK invoice, and the Invoice Register totalling a saved EU invoice.
Calculator tab - UK region, principal, interest and compensation broken out
Invoice Register - saved invoices tagged by region, with a running total
Pick UK, Ireland/EU, Australia, US, Canada, New Zealand, or a fully custom region, and the calculator sets a sensible default reference rate, margin, currency symbol and compensation rule - every default stays editable so you can correct it against your own current source.
A reference rate plus your margin, applied to the invoice amount for exactly the number of days it's overdue - in the UK that's the Bank of England base rate plus 8 percentage points under the Late Payment of Commercial Debts (Interest) Act 1998; other regions get their own default, or set your own.
UK debts get £40/£70/£100 banded by size under the 2013 Regulations, EU debts get a flat €40 minimum, other regions default to none unless you set your own flat amount in Custom mode - added on top of interest without you having to look anything up.
Principal, interest and compensation as three segments of a single bar, so you can see at a glance how much of what's owed is the original invoice and how much is the cost of being paid late.
Leave the payment date blank for an invoice that's still outstanding - interest keeps running against today's date every time you open the calculator - or enter the date it was actually settled for a fixed final figure.
Save every overdue invoice you're chasing with a reference name, and the register recalculates each one's interest live and shows a running total across all of them - useful when you're chasing more than one late payer, in more than one country, at once.
Every unpaid invoice past its due date is flagged clearly in the register, so you can see which ones need chasing without re-checking dates by hand.
Not construction-gated - works for any UK business chasing an overdue B2B invoice, whatever the trade or industry.
A light/dark toggle that remembers your choice, and "Load sample" fills in a realistic overdue invoice so you can see the calculation before entering your own numbers.
Chaser is a well-known credit control platform - automated chasing emails, a dedicated payment portal and reporting - priced per user per month. Here's how a focused, one-off interest calculator compares for a business that just needs to work out what's owed.
| Feature | Late Payment Interest Calculator | Chaser |
|---|---|---|
| Pricing model | £0.79 one-off after trial | From around £39/user/month billed annually |
| Works fully offline | ✓ | ✕ |
| Interest & compensation calculation, with region presets | ✓ | ✕ |
| Running total across multiple overdue invoices | ✓ | ✓ |
| Automated chasing emails and payment portal | ✕ | ✓ |
| Accounting software integration | ✕ | ✓ |
| Single-purpose, no unrelated features to learn | ✓ | ✕ |
Comparison based on Chaser's publicly listed pricing and features as of August 2026 (chaserhq.com) - pricing and features change over time, so check chaserhq.com for current details. Chaser is a trademark of its respective owner; this comparison is for informational purposes and isn't sponsored by or affiliated with Chaser.
Late Payment Interest Calculator is a Windows desktop app, free to try from the Microsoft Store.
The UK, Ireland/EU, Australia, US, Canada and New Zealand each have a preset for their typical reference rate, margin, currency and compensation rule, plus a fully custom mode for any other country. Every default stays editable so you can correct it against your own current source.
Interest is the reference rate plus your margin, applied to the invoice amount for every day it's overdue. In the UK that's the Bank of England base rate plus 8 percentage points under the Late Payment of Commercial Debts (Interest) Act 1998; other regions have their own default rate and margin, or you can set your own. Interest runs from the day after the due date up to the date paid, or today if it's still unpaid.
It depends on the region. The UK bands it by debt size: £40 under £1,000, £70 from £1,000 to £9,999.99, and £100 at £10,000 or more, under the Late Payment of Commercial Debts Regulations 2013. The EU sets a flat €40 minimum under the Late Payment Directive. Other regions have no fixed statutory sum by default, though you can set your own flat amount in Custom mode. It's payable in addition to interest once a debt is overdue.
The regional presets are aimed at business-to-business commercial debts, not consumer debts, and most late-payment regimes apply by default unless the contract sets a substantial alternative remedy. Rules vary significantly by country - check your own region's current law before relying on this figure.
Save every overdue invoice you're chasing and the register recalculates each one's interest live against today's date, showing a running total of everything you're owed across all of them.
Everything persists on your device between sessions - nothing is uploaded anywhere. Data doesn't currently sync across multiple devices.
No - it's a calculator to help you work out a figure, not legal or financial advice. Always check your numbers, and take professional advice before pursuing a debt formally.