AnswersWhen a client won't pay
Why do clients pay late, and what do I do about each reason?
The short answer
Four reasons. Cash flow, process, dispute or habit, and each needs a different reply. Interest runs from the day after the due date4 whatever the cause, so the clock does not wait for you to find out which. For a large client the answer is partly public: it must publish a payment report at least twice a year1, with the average days it takes to pay2.
What you can add
A £4,200 invoice, 35 days late
Say you invoiced another business £4,200 for design work, due on 31 July 2026. It was paid on 4 September 2026: 35 days late, and late from 1 August. Bank Rate was 3.75% on 30 June, so the rate is 8% above it8, 11.75% a year9.
The extras come to £117.32: £47.32 of interest, which grew by £1.35 a day while it was unpaid, and the £70.00 fixed sum. Their reason decides your reply. Their cash flow or their habits do not cut the sum; your own conduct5 can.
The road ahead
Three steps, then one of four replies.
Step 1: Check your own invoice first
Look for the usual faults: the wrong company name, no order number, the wrong person or address, or an invoice sent weeks after the work. Where no date was agreed, the 30 days start from the later of the work done and the customer having notice of the amount4, so a late invoice moves your date, and so can one sent to the wrong company or for the wrong amount.
Interest can also be cut where the supplier's own conduct5 makes that fair. Fix your side before you ask anything of theirs.
Step 2: Look up a large client's payment report
A company or LLP with at least two of £54 million turnover, £27 million on the balance sheet, 250 employees1 must publish one. GOV.UK lets you download every published report.
It gives the average days to pay and the share paid late2, whether it takes invoices electronically2, and how it settles payment disputes2.
A high late share suggests habit; a low one makes habit less likely. Reports for years from 2025 also give the share late because of a dispute3, so set that part aside. A record is a guide to this client, not a verdict on anyone.
Step 3: Send the one question
Email the letter below to your contact and the accounts address. Late payment can have honest causes, from financial difficulties to administrative errors10, and one reply or one silence sorts yours into one of the four below.
Step 4: Cash flow: get a date and a part-payment
Clues: part-payments, short answers, "once the money comes in". Ask for a date in writing and for what they can pay now. If they want longer, a short written plan can work, and checking the company shows how far to trust it.
Step 5: Process: remove the blocker today
Clues: a missing purchase order, approval waiting, a rejected upload, the wrong address. Send the number, reissue to the right name or address, and ask who approves it and when the next payment run is. What "pending approval" really means shows what to ask.
Step 6: Dispute: get the reason in writing
Clue: "something is wrong" with the work or the invoice. Ask for the reason in writing and ask them to pay the part they do not dispute now. Hold the interest demand until you have read the reason; sent first, it turns a question into an argument.
Step 7: Habit: add the interest and change your terms
Clue: they pay late to everyone, or to you every time. Send the interest and fixed-sum wording, then shorten your terms or ask for a deposit on the next job. The first-move page covers the first letter.
A letter you can copy
Email asking what is stopping payment
Send it at day 7, as the first reminder, to the person who approves payments and the accounts address, before you pick a reply.
Tap a highlighted gap to see what goes in it.
Send it to the approver and the accounts address together, so neither can say it did not arrive. Keep the sent email with the invoice. Silence for a week is an answer too: nobody is working on your invoice. Ring the contact and ask the same two questions.
When not to bother
When it isn't worth it
- It is their first slip and the record is clean. A short nudge is enough. Skip the diagnosis.
- The company looks like it is failing. The reason matters less than the queue for the money. Check the company first.
- The cause is your own invoice. Correct it and send it again before anything on this page. The start of interest may move with it.
- The client is a consumer, not a business. Consumer debts work differently, and these pages do not cover them.
The Wolf's note
Ask one question and the reply sorts the invoice. Silence is a reply too. Answer the reason you find, not the one you assumed, because the interest clock runs while you decide.
Mr. Wolf · the AI inside WolfX
What comes next
Your next move
My client has gone quiet. How do I get an answer?
Ask someone else: ring accounts payable, email a second name, then post to the registered office, which the law counts as delivery to the company.
6 min read · Letter included
My client keeps promising to pay but never does. What now?
Stop collecting promises.
6 min read · Letter included
A struggling client wants a payment plan. Should I agree, and how do I set one up?
Yes, with money on signing, a signed written plan and a clause making the whole balance due if a payment is missed.
7 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.