Late Payment Calculator
1 credit / callWhat a late-paid business invoice is owed: statutory interest at the right rate for each half-year, plus the fixed compensation.
Interest at 8% over the reference Bank Rate, by the day, per half-year; the fixed compensation; the per-day figure while unpaid. The Bank's rate read daily from its own page.
Under the Late Payment of Commercial Debts (Interest) Act 1998 a business that's paid late may charge statutory interest at 8% over the Bank of England's Bank Rate, and add a fixed sum per invoice (£40, £70 or £100 by its size). The catch people get wrong: the rate isn't today's Bank Rate but the rate on the previous 30 June or 31 December, each half-year on its own, so an invoice late across the new year runs at two rates. This endpoint reads the Bank's own rate page daily, works the interest by the day for each half-year, adds the compensation, and gives the per-day figure for an invoice still unpaid. Business-to-business, where the contract sets no other rate. Not legal advice; it says so.
what you’d build with it
Invoicing and accounting software
The exact statutory sum on every overdue invoice, with the reference-rate basis spelled out.
Debt recovery and credit control
The figure for the letter before action, the day it's sent.
Small businesses
What you're owed, in one call, before you decide whether to claim it.
example response
{
"invoice": { "amount": 5000, "due": "2025-12-01", "paid": "2026-01-30" },
"late": true,
"daysLate": 60,
"statutoryInterest": 98.63,
"fixedCompensation": 70,
"total": 168.63,
…Abbreviated. The full example, every endpoint and runnable code are in the implementation guide above; the integration pack downloads beside it. No account needed to read any of it.
Why developers pick it
The right rate, by half-year
The reference Bank Rate on 30 June or 31 December, each period on its own, not today's rate applied to the lot.
The Bank's own page, daily
No hard-coded rate to go stale; every reply says when the rate was read.
Per-day while unpaid
The sum today and what it grows by tomorrow, for the chasing letter.
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