If you are a business owed money by another business, the UK and the EU both give you a statutory right to interest on a late commercial invoice, even when the contract never mentioned a late fee. You can also claim a fixed sum for the cost of chasing it. The right is not a mood and it is not a 1.5% line you invent on day 40. It is a formula, and the formula is different in London, in the euro area, and in Oslo.
Consumer debts, rent, and wages sit under other rules. If one side is a private person buying as a consumer, stop and get advice before you quote a statute. The rest of this piece is about business-to-business invoices.
United Kingdom: the 1998 Act
The Late Payment of Commercial Debts (Interest) Act 1998 is the UK statute. Statutory interest is 8 percentage points above the Bank of England base rate for the period the debt is late. On 16 September 2026 the Bank's Monetary Policy Committee voted to hold Bank Rate at 3.75%. Eight points on top of 3.75% is 11.75% a year. If the Bank changes Bank Rate, this percentage changes with it. It is not frozen for a half-year the way the EU reference rate is.
The official sources are the Act itself on legislation.gov.uk and the GOV.UK page 'Late commercial payments: charging interest and debt recovery.' Use those, not a screenshot of a forum. The Bank's September 2026 monetary policy summary is the source for 3.75%.
On top of interest, section 5A gives a fixed sum once statutory interest starts, once per qualifying debt. Under £1,000, the sum is £40. From £1,000 up to but not including £10,000, it is £70. At £10,000 and above, it is £100. If your reasonable recovery costs are higher than that fixed sum, the Act lets you claim the difference. 'Reasonable' means costs you can explain, not a round number that appeared because you were annoyed.
The EU directive, and why countries still differ
Directive 2011/7/EU on combating late payment in commercial transactions is the European floor. Interest must be at least the reference rate plus 8 percentage points. Compensation for recovery costs must be at least €40. The text is on EUR-Lex. Member states implement it, so France, Germany, Ireland, and Spain are not interchangeable. Some set a higher margin. Some use a national base rate instead of the ECB rate. A tool that only shows the floor will understate a French claim and will not invent a German one.
For euro-area countries, the reference rate is the European Central Bank's main refinancing rate in force on 1 January or 1 July, and it governs that half-year. On 1 July 2026 that rate was 2.40%, the level set with effect from 17 June 2026. The ECB's own key-rates table shows a later rise to 2.65% from 16 September 2026. That September rise does not rewrite the 1 July reference. The Directive minimum for 1 July to 31 December 2026 is 2.40% plus 8 points, which is 10.40% a year, plus at least €40. The next reset is 1 January 2027.
If you invoice from, or into, a country that publishes a higher rate, use that rate. The UK and EU calculator lets you override the base figure so you are not stuck with the floor when you have checked the national number.
Norway: forsinkelsesrente and the reminder fee
Norway is not in the EU. It follows the idea through the EEA and its own statute, lov 17. desember 1976 nr. 100, forsinkelsesrenteloven, which is on Lovdata. The rate is set twice a year, from 1 January and 1 July. Finansdepartementet delegated the setting of the rate to Finanstilsynet in June 2025. Finanstilsynet's notice for the second half of 2026 sets forsinkelsesrente at 12.25% a year, and standard compensation for recovery costs at NOK 430. The law requires the rate to be Norges Bank's policy rate plus at least 8 percentage points. Use the published 12.25%, not a rate you recompute in the middle of the half-year because the policy rate twitched.
A purregebyr is a reminder fee. It is a contractual or debt-collection charge, not the same thing as the NOK 430 statutory compensation. If your terms never named a purregebyr, do not add one because a template suggested it. The 12.25% and the NOK 430 are the statutory pieces. Anything else needs a sentence the client already accepted.
A worked example: £3,000, 45 days late
Assume a UK commercial invoice for £3,000, due on a date that is now 45 days ago, and Bank Rate is still 3.75%. Statutory rate: 3.75% + 8% = 11.75% a year. Day count: 365.
- Yearly interest on the debt: £3,000 × 0.1175 = £352.50.
- Daily interest: £352.50 / 365 = £0.965753.
- Interest for 45 days: £0.965753 × 45 = £43.4589, which is £43.46 to the penny.
- Fixed compensation: the debt is over £1,000 and under £10,000, so £70.
- Interest plus compensation: £43.46 + £70 = £113.46, claimed on top of the £3,000.
If you were using the EU floor instead, the same £3,000 is the wrong currency, so do not paste this example onto a euro invoice. On €3,000 at 10.40% for 45 days: €3,000 × 0.104 / 365 × 45 = €38.47 of interest, plus at least €40 compensation. Different country, different statute, different total. The contractual late fee calculator is for a percent you wrote in the terms. Do not mix that 1.5% a month with this statutory formula on the same demand unless you know which one you are legally using.
How to claim it in the email
Name the invoice, the principal, the days, the rate, the interest, and the fixed sum. Offer the principal alone if they pay by a date you would actually accept. That is a waiver, and it should be explicit.
Hi Priya, Invoice 1842 for £3,000 was due on 12 August 2026 and is 45 days overdue. Statutory interest under the Late Payment of Commercial Debts (Interest) Act 1998 is 8 percentage points above Bank Rate. Bank Rate is 3.75%, so the rate is 11.75% a year. £3,000 × 11.75% × 45 / 365 = £43.46 interest. The fixed compensation for a debt of this size is £70. The total if it remains unpaid is £3,113.46. If you pay the original £3,000 by Friday 9 October 2026, I will waive the interest and the £70 on this invoice. Thanks, Abass
Change the dates and the Bank Rate if they have moved. Do not send this wording on a consumer invoice. If they are in another country, name that country's rule or stay quiet until you have checked it. The client won't pay templates cover the chase before you reach for a statute. Statutory interest is a later sentence, not the first nudge.
When it is worth claiming, and when it is not
It is worth claiming when the client is a business, the delay is measured in weeks not hours, you have already sent the invoice to the right person, and you are willing to stand behind the number. £43 is not a relationship strategy. It is a price for 45 days of someone else's cash. On a client who pays you every month and slipped once, waive it and keep the work. On a client who treats Net 30 as Net whenever, the statute is one of the few sentences that is not a matter of your confidence.
It is not worth claiming when you cannot show the invoice was due, when the debt is genuinely disputed, or when you are using the percentage to punish a tone you did not like in an email. Interest on a disputed principal is how a small claim gets messier. Settle the principal first if the argument is about the work.
Why the contract clause still helps
The statute is the backstop. The clause is how you avoid explaining a statute to a client who would have paid a number they already signed. A clause can set a grace period, a simpler fee, and a pause-work rule. The guide to charging late fees is about that contractual version. Keep it consistent. If your contract says 1.5% a month and the statute says 11.75% a year, know which one you are invoicing. You generally claim one remedy, not a stack of every number you can find.
The same 45 days at three debt sizes
The £3,000 example is the middle tier. The edges are worth seeing, because the fixed sum jumps and the interest does not feel the way people guess. Take the UK rate used on this page, 11.75% a year, 365-day count, 45 days late. On £800, which is under £1,000, interest is £800 × 0.1175 / 365 × 45 = £11.59. The fixed sum is £40. Interest plus compensation is £51.59. On £12,000, which is £10,000 or more, interest is £12,000 × 0.1175 / 365 × 45 = £173.84. The fixed sum is £100. Interest plus compensation is £273.84. Round to the penny at the end.
Norway, on the rate Finanstilsynet published for 1 July to 31 December 2026, is a different currency and a different fixed sum. A NOK 10,000 invoice, 30 days late, at 12.25% is 10,000 × 0.1225 / 365 × 30 = NOK 100.68 of interest, plus standard compensation of NOK 430, so NOK 530.68 on top of the principal if the debt qualifies. That 430 is not a reminder fee you invented. A purregebyr still has to come from the contract. Do not add a second flat fee because both words exist.
The EU floor on the same shape, €3,000 for 45 days at 10.40%, is €3,000 × 0.104 / 365 × 45 = €38.47, plus the Directive's minimum €40, so €78.47 of statutory add-on before any higher national margin. Germany and France may allow more than 8 points. This page will not pretend their margin is the floor. If you invoice there, read the national rule or type the rate you have checked into the calculator's override.
What to recheck on the morning you send the figure
Three dates, not a vibe. For a UK invoice, the Bank of England Bank Rate in force over the late period, because statutory interest there tracks the current base rate rather than a half-year freeze. For an EU invoice, the reference rate that was fixed on the previous 1 January or 1 July, which can differ from the ECB rate announced last week. For Norway, the forsinkelsesrente notice that covers the half-year you are in. The sources are linked above. A blog that repeats them is not a source.
Then check the debtor. A limited company, a partnership, or another trader can sit inside these commercial rules. A private individual paying you for something that is not their business often cannot. If you are unsure which one they are, do not send the statutory paragraph. Send the principal, the due date, and a request for a payment date. You can add interest after a qualified person tells you the debt qualifies. You cannot unsend a percentage.
If you want the arithmetic without retyping it, the calculator on this site uses the same inputs as this page: the stored base rate, the statutory margin, a 365-day year, and the fixed sum for the debt size. Override the base rate when you have checked a newer figure than the one printed beside the result. Do not override it to make the number larger. A claim you cannot recompute on paper is a claim you should not send.
Put the clause in the next contract even though the right can exist without it. Then, if you ever need the statute, you will look like a business that priced lateness in advance, not a business that discovered legislation in the middle of a chase. Recheck the Bank Rate, the ECB 1 January or 1 July reference, and the Norwegian half-year notice before you send the email. Those three numbers move. The Acts do not care what this page said last spring.