Can I waive the interest now and still claim it later?
The short answer
Yes, if reserved. The right to interest is built into the contract by the Act1, so silence, or leaving it off an invoice, does not lose it. What loses it is an agreement to drop it, and the Act lets you make one once the debt exists3. The right lasts six years5 from the due date; “I reserve the right to claim interest” puts that on the record, and an agreed “no interest will be added” usually ends it.
England and Wales only. WolfX is software, not a law firm.
What you can add
A £5,500 invoice, 63 days late
Say you invoiced another business £5,500 for consulting, due on 10 July 2026. Interest starts the day after2, so it is late from 11 July. On 11 September it is unpaid: 63 days late, and the client asks you not to bother with interest. The invoice went late in the second half of 2026, so the rate is 8% plus the 3.75% Bank Rate9 on 30 June 2026.
Then it grows by £1.77 a day until they pay. “No interest will be added” would give up all of it, for one sentence.
The road ahead
Five steps. All free.
Step 1: Check what you have already said
Step 2: Pick the wording that does what you mean
To keep it: “I have not added interest to this invoice. I reserve the right to claim statutory interest and the fixed sum on it, and on any later late payment.” It states your right and asks them for nothing extra today.
To give it up: “No interest will be added to this invoice” or “interest waived”. Written down, that is the kind of agreement the Act allows3, and you should expect to be held to it.
Step 3: Name the invoice and both sums
Put the invoice number in, so a waiver cannot be read as covering the next one. Interest and the fixed sum7 are separate rights, so say which you are giving up.
Step 4: Or waive on a condition
To be kind and get paid, tie it to a date: “No interest on invoice 4502 if it is paid in full by 24 September 2026.” If the date passes unpaid, the condition has failed and the right is usually still there.
Step 5: Send it in writing and keep a copy
Email it, so it is dated. In England and Wales, interest on each invoice can be claimed for six years5 from when the claim arose, usually the day payment fell due, so reserving it costs nothing. For the claim itself, see interest on invoices already paid late.
A letter you can copy
Email reserving your right to interest
Send it when you are letting a payment slide, or have said nothing about interest, and want to keep the right.
Tap a highlighted gap to see what goes in it.
Send it by email so it is dated, and keep a copy with the invoice. Repeat the reservation line on any reminder you send later, so it stays on the record.
When not to bother
When it isn't worth it
- A first slip by a client you want to keep. Waive it on purpose, in writing, naming the invoice and saying it is for this one only.
- The sum is smaller than the goodwill. A few days late is pennies of interest. Say “no interest on invoice 4502” and move on.
- You are settling the whole debt. “In full and final settlement” wording ends the entire claim, interest included, so read it before you agree to it.
- Your contract already sets a late fee. If it is a substantial one, it applies instead4 of the Act's interest.
- You are waiting for a new law. A Bill before Parliament would mandate late payment interest10, but is not law on 8 October 2026 and will not reach invoices already late. Reserve now.
The Wolf's note
Kind and careful need different sentences. One keeps the right and says so; the other ends it. Decide which you mean before you press send.
Mr. Wolf · the AI inside WolfX
What comes next
Your next move
Can I claim interest on invoices my client already paid late?
Usually. Being paid does not end the right to interest and a fixed sum of £40, £70 or £100 per invoice, and you can claim up to six years back.
6 min read · Letter included
Should I charge interest at all, or does it backfire?
Yes for a habit, not for a first slip.
5 min read · Letter included
My client refuses to pay the interest. What then?
Still owed. A refusal does not remove late payment interest or the fixed sum.
6 min read · Letter included
Don't want to do this yourself?
The Wolf does every step for you. He works out the sums, writes the letters and keeps track of every date. Nothing goes without your yes.