UK and EU late payment interest calculator

This is general information, not legal or tax advice. Rules vary by jurisdiction and change. Consult a qualified professional for your situation.

Most freelancers never use the statutory right because they think a late fee has to be in the contract or it does not exist. On a commercial invoice, the UK Act and the EU Directive both create a right that does not depend on that clause. The calculator applies the stored rates and shows the arithmetic. It does not decide whether your invoice qualifies.

Contractual interest is the percent you wrote down before the work. Statutory interest is the percent the law names when you did not, or when the contract’s alternative is not a substantial remedy. They are different numbers. The guide to late payment rights walks through the Acts. The guide to charging late fees walks through the clause. Use the matching calculator. Do not add the outputs together.

How to claim it, and when not to

Put the invoice number, the principal, the days, the rate, the daily math, and the fixed sum in the email. Offer to waive the interest if they pay the principal by a real date. A waiver you mean is cleaner than a percentage you will never enforce. If they pay the principal and ignore the interest, decide once: chase the interest, or waive it in writing. Do not leave it implied.

Claiming a small statutory sum can sour a client who is merely slow. Not claiming it can teach a commercial client that dates are decorative. The test I use is whether you would also pause new work. If the relationship is worth more than the interest, waive it and tighten the next deposit. If the client has gone quiet after receiving the invoice, the templates for a client who will not pay come before a statutory demand, not after you have already threatened a percent you cannot explain.

What the result is showing you

Days overdue are counted from the due date to the day you say you were paid, or to today if the invoice is still open. A future due date produces nothing to claim. The rate line splits the figure into a base rate and the statutory margin, and it prints the dates those inputs are effective. Interest is simple, not compounded: amount times the annual rate, divided by 365, times the days. The page shows that daily rate so you can redo it on paper before you put it in an email.

Fixed compensation is a separate sum, not a second interest rate. In the UK it is £40, £70, or £100 by the size of the debt. Across the Directive it is at least €40, and several countries set their own currency amount. Norway’s published standard compensation for the second half of 2026 is NOK 430. The total claimable line adds interest and that fixed sum to the principal only as a way to see the whole demand. You can still choose to waive the add-on and collect the invoice alone.

Sweden and Denmark are listed because people search for them, and the row is honest about being the Directive floor. Type the national reference rate if you have it. Germany and France may use a higher margin than 8 points. The calculator will not invent those margins. An override field is there so a checked number beats a stored floor. If you leave the override blank, you are using the config, and the config’s dates are part of the answer.

Check the figure on paper before you send it

A £3,000 UK commercial invoice, 45 days late, at 11.75%, is £3,000 × 0.1175 / 365 = £0.9658 a day, times 45, which is £43.46. The debt is between £1,000 and £10,000, so the fixed sum is £70. Interest plus compensation is £113.46. If the invoice is still unpaid, the demand for principal plus those two amounts is £3,113.46. Run that invoice through the form and you should see the same pennies. If you do not, the base rate in the config has moved, or you typed a different day count. Do not email a number you cannot reproduce.

The same shape on the EU floor is a different rate on purpose. €3,000 for 45 days at 10.40% is €3,000 × 0.104 / 365 × 45 = €38.47, plus at least €40. That 10.40% is 2.40 plus 8, and 2.40 was the ECB main refinancing rate in force on 1 July 2026. The September rise to 2.65% does not rewrite the half-year reference. If your member state uses a higher margin, the floor is the wrong number to claim and the right number to start from. Override it. Say which rule you used in the email.

Norway is not the EU floor. The published forsinkelsesrente for 1 July to 31 December 2026 is 12.25% a year, and the standard compensation published with it is NOK 430. A reminder fee you agreed in a contract is extra only if the contract says so. The calculator will not add one. If you want that fee, put it in the letter yourself and be ready to point at the clause.

Still unpaid means the end date is today, so the total grows by the daily rate each morning. Payment received means you stop the count on that day. Do not count both a contractual late fee and this statutory interest on the same demand unless a qualified person has told you that you may. The other calculator on this site is for the percent you wrote down. This one is for the statute. Pick one story and tell it completely.

Rates live in a config file so the next Bank Rate move is an edit, not a hunt through the component. The result tells you the date the figure is in force from, and the date by which you should recheck it. If those dates are behind the central bank’s latest note, do not send the email until you have checked. A confident wrong rate is worse than no rate.