A payment term gets honoured when your customer agreed to it before the work started, can tell from your invoice exactly what date the money has to move, and has a way of paying that takes seconds. In Adfin's own book the invoices paid on time least often are the ones due the day they were issued, at 59.5%, against 76.4% for terms of 8 to 14 days (Adfin platform data, 59,777 paid customer-initiated invoices over 26 months).
In this article
The short version
- Agreed terms govern. With nothing agreed, the Late Payment of Commercial Debts (Interest) Act 1998 supplies 30 days.
- A public authority's payment period cannot fall later than 30 days, and for a private purchaser a period beyond 60 days stands only where it is "not grossly unfair to the supplier", under section 4 of that Act.
- The 30 days runs from the later of performance and notice of the amount, so a late invoice delays your own clock.
- On-time payment rises with the length of terms in Adfin's data, from 59.5% on same-day terms to 76.4% at 8 to 14 days (Adfin platform data, 59,777 paid customer-initiated invoices). The relationship is an association and probably selection, and nobody's tested whether changing your terms changes the result.
- 5.5% of those invoices went out with a due date already in the past (Adfin platform data).
- A weekend due date is paid on time about six percent less often than a weekday one (Adfin platform data).
What makes a payment term enforceable
Two questions hide inside "payment terms": whether a term binds your customer, and whether they honour it. The legal half is settled and short.
Agreed terms govern. Where you and your customer agreed 14 days, 14 days applies. Where nothing was agreed, the Late Payment of Commercial Debts (Interest) Act 1998 supplies a 30 day period, and section 4 of that Act limits how far an agreement can push that out:
| Situation | The position |
|---|---|
| Terms agreed with a business customer | The agreed period applies |
| Nothing agreed | 30 days, from the later of performance and notice of the amount |
| A public authority | The relevant day cannot fall later than 30 days |
| A private purchaser beyond 60 days | Stands only where the period is "not grossly unfair to the supplier" |
Three practical consequences follow. Your clock starts at the later of doing the work and telling your customer what they owe, so an invoice raised a fortnight after delivery has cost you a fortnight. Statutory interest at base rate plus 8% runs from the day after your due date whether or not your contract mentions it, currently 11.75%, with fixed compensation alongside it in what you can charge on an overdue invoice. And a client pushing for 60 days is asking for something the law allows, so your answer to that is commercial: how to invoice a client who insists on 60-day terms takes it apart.
Short terms go with worse on-time payment, not better
Tight terms feel like the safe choice, and Adfin's own invoices point the other way. Across 59,777 paid invoices where the customer chose when to act, on-time payment rises with the term: 59.5% where the invoice was due the day it was issued, 70.9% at 1 to 7 days, and 76.4% at 8 to 14 days, after which it flattens out between about 74% and 76% through to 60 days (Adfin platform data). Full bands are in the UK Getting Paid Report.
Does that mean longer terms would get you paid sooner? The figures can't show that. Terms here are inferred from the gap between the invoice date and the due date, and nobody moved a due date and watched what happened. The likeliest explanation is selection: a business that sets a considered 14 day term tends to bill promptly and follow up as well, so their terms look like a symptom of that habit and not its cause. So the data can tell you that giving your customer a fortnight doesn't appear to make them slower, and it can't tell you that extending your own terms would improve your on-time rate.
A trade-off is visible in the same data. Longer terms bring a longer wait on the invoices that do go late: a median of 5 days late on same-day terms against 9 at 8 to 14 days and 11 at 31 to 60 days (Adfin platform data).
What survives the hedging is still useful to you: same-day terms don't appear to buy the speed they promise, so if your invoices go out due immediately because that's how your template was set up, there's no support here for keeping it that way.
The 5.5% of invoices that were never going to be on time
One category needs no interpretation. Of those 59,777 invoices, 3,271 went out with a due date already in the past, so none could be paid on time and their median delay was 42 days (Adfin platform data).
Some of that is back-dated or catch-up invoicing entered after the money was already agreed, and the warehouse can't separate those from an invoice raised live and already overdue. Either way, a term that expired before your customer saw it gives them nothing to aim at, and your ageing report describes your admin instead of their behaviour.
The fix is usually mechanical: where invoices come from timesheets or a monthly close, calculate the due date at the moment of issue instead of carrying it over from the period the work covered.
Weekend due dates cost you about six percent
Your due date's day of the week has a measurable association with whether it gets met. Invoices due Monday to Friday were paid on time 65.8% to 67.2% of the time; Saturday ran at 60.4% and Sunday at 60.6% (Adfin platform data, 59,777 paid customer-initiated invoices, 4,372 due on a Saturday and 3,611 on a Sunday). The weekend confidence intervals don't overlap any weekday interval.
The likeliest mechanism is mechanical: a Saturday deadline means Friday was the last working day your customer had to act, so your term is shorter than it looks. That reading is an inference, and the finding is still association, since nobody has moved a batch of due dates from Saturday to Friday and measured the difference.
It's cheap to act on regardless. If your terms run a fixed number of days from issue, roughly two in seven of your due dates land at a weekend without anybody choosing it, and rounding to the nearest working day costs you nothing.
Writing a term your customer can act on
Once the legal side holds, the rest is about how little work your invoice leaves the person paying it.
- Give a date, not a duration. "Due 14 September 2026" needs no arithmetic, and no guess about whether your 14 days started at delivery or when their system logged the invoice.
- Agree the term before the work, in writing, and use the same words on your engagement letter and your invoice. A term that first appears on the invoice can be disputed at exactly the wrong moment.
- Put the amount and the reference where a finance team can find them, since a payment run matches on those. What to include on a UK invoice covers the required fields.
- Attach the way to pay to the invoice itself. Payments in Adfin's book cluster on the due date, so your invoice needs to be payable at the moment your customer finally looks at it.
- Say what happens after the date in one sentence, and apply it consistently. How to apply late payment fees automatically covers doing that without a monthly decision.
- Ask who processes payments and when their runs happen. A customer paying on the 25th will honour a 25th due date and miss a 20th, and that's scheduling, not negotiation.
When the term needs a mandate behind it
For a client who agrees your terms every quarter and misses them every quarter, rewording the term is unlikely to change much. A direct debit mandate changes what your term means: you give notice of the amount and the date, the collection happens then, and your client's diary stops being part of it.
Two caveats come with that. A mandate takes time and your client's agreement, and it changes what your reports can tell you, because a Bacs collection settles a few days after your due date by design. Compare direct debit only with direct debit, and keep it out of any on-time average with card or transfer payments: which methods can be compared on time works through why, and direct debit for UK businesses covers mandates and notice.
The supporting pattern is about resolution and not lateness. Where a mandate existed when the invoice was raised, 97.0% of invoices were paid and 1.3% were still unresolved six or more months later, against 90.3% and 5.4% where there was none (Adfin platform data, 152,689 invoices raised in the seven months to 31 January 2026). That's an association too: a client willing to sign a mandate may well have been one who'd have paid you anyway.
Common questions
What payment terms should I set? Legally you can set what your customer agrees to, and 30 days applies where nothing is agreed. In Adfin's data invoices due 8 to 14 days after issue were paid on time 76.4% of the time against 59.5% for those due the day they were issued, on 59,777 paid customer-initiated invoices. That's an association and not a tested effect, so read it as a reason to look again at same-day terms.
Do longer payment terms mean slower payment? Not in this data. On-time payment rises from 59.5% on same-day terms to 76.4% at 8 to 14 days and then flattens out to 60 days. The trade-off is on the invoices that do go late, where the median delay grows from 5 days on same-day terms to 11 days at 31 to 60 days.
Can a customer insist on 60-day terms? They can ask, and you can agree. For a private-sector purchaser a period longer than 60 days stands only where it is not grossly unfair to you, and a public authority's period cannot fall later than 30 days. Statutory interest still runs from the day after whatever date you agreed.
When does the payment clock start, the invoice date or the delivery date? Where no term is agreed, the 30 days runs from the later of performance and the day your customer was told what they owe, so invoicing a fortnight after delivery pushes your own due date out by a fortnight.
Why do invoices with a weekend due date get paid late more often? An invoice due on a Saturday or Sunday was paid on time 60.4% and 60.6% of the time against 65.8% to 67.2% Monday to Friday. The likeliest reason is that Friday was your customer's last working day to act. Nobody has tested whether moving the date causes the improvement.
How do I stop invoices going out already overdue? Calculate the due date from the issue date at the moment of issue, instead of from the period the work covered. In Adfin's book 5.5% of customer-initiated invoices carried a due date already in the past, and their median delay was 42 days.
Sources
- legislation.gov.uk — Late Payment of Commercial Debts (Interest) Act 1998, section 4 (accurate as of August 2026)
- GOV.UK — Charging interest on a commercial debt (accurate as of August 2026)
This article is general information about UK payment terms and is not legal advice. Figures from Adfin's platform describe customer-initiated payments only, and the relationships between terms, due dates and on-time payment described here are associations and not tested effects. Last updated August 2026.
