In Adfin's payment data, direct debit collects about 95% of requests whether the invoice is under £100 or over £2,500, so large invoices are no harder to collect that way. They're far less likely to have a mandate behind them, though: about three quarters of paid invoices under £100 had one, against just over a third of those at £2,500 or more. That leaves the biggest invoices the most likely to depend on someone chasing.
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The short version
- In Adfin's data, direct debit collects about 95% of requests whatever the invoice size.
- Mandate coverage halves from 74.1% under £100 to 37.4% at £2,500 and over.
- Large invoices with a mandate are paid another way about three times as often.
- Ask for the mandate while the price is agreed, and check coverage by invoice size.
- One mandate can collect varying amounts with advance notice.
Are bigger invoices harder to collect?
You'd expect them to be. A larger amount needs approval, and it competes with everything else your customer owes that month. Adfin's own payment data, which covers mostly small-ticket UK invoices, only partly bears that out.
When your customers choose when to pay, by card, bank transfer or pay by bank, bigger invoices are late a little more often: 41.3% of those at £2,500 or more were paid after the due date, against 30.4% under £100. But among the ones that were late, the typical delay was the same eight days at every size. Much of the gap also comes from the mix of businesses, because firms that issue large invoices work in different sectors, with different customers. If you compare small and large invoices within the same business, the difference mostly shrinks away.
Direct debit shows almost no size effect. It collects between 94.5% and 95.5% of requests in every band from under £100 to over £2,500, and the largest band had the lowest rate of failed attempts, at 1.7%. So a £3,000 collection is no harder for you to take than a £50 one.
How mandate coverage falls as invoices grow
Size does make a difference to whether a mandate is in place. Take the paid invoices in the data and ask whether the customer had a direct debit mandate when each one was raised:
| Invoice value | Mandate in place | Of those with a mandate, paid another way |
|---|---|---|
| Under £100 | 74.1% | 8.4% |
| £100 to £249 | 69.7% | 8.5% |
| £250 to £499 | 64.0% | 9.4% |
| £500 to £999 | 58.4% | 12.2% |
| £1,000 to £2,499 | 49.1% | 19.7% |
| £2,500 and over | 37.4% | 24.3% |
Coverage halves from the smallest band to the largest. And even where there's a mandate, large invoices leave it about three times as often: almost a quarter of the largest went another way, against fewer than one in ten of the smallest. If that matches your own book, your biggest invoices are the ones you're chasing by hand.
Some of that pattern also reflects which businesses issue large invoices. Within a single business the gap's smaller, but about two thirds of businesses whose coverage differed between their small and large invoices covered the large ones less.
These figures describe a pattern in one platform's data, not a cause, so treat them as a direction to check against your own book.
Why large invoices end up off direct debit
The data records what happened, not why. These are the likeliest explanations, and in your business it's probably a mix.
- Mandates come with recurring work. Your monthly retainer gets a mandate at the start, while a project fee or an annual renewal often arrives later, with no obvious moment for anyone to set one up.
- Comfort levels differ. A finance team that's relaxed about £150 a month leaving automatically may feel differently about £4,000, even with advance notice.
- Large invoices are more often under discussion, and you don't want an automatic collection landing while the amount is still being agreed.
- Some providers charge more for high-value collections or set limits, which nudges bigger amounts onto card or bank transfer.
Any of those can be a sensible choice for a particular invoice, but together they leave your largest invoices, often a big share of what you're owed, depending on you sending a reminder and your customer remembering to act on it.
How to get a mandate behind your larger invoices
Start by checking your own mandate coverage by invoice size, not just overall. A healthy headline figure can hide a top band that you're chasing entirely by hand.
Then look at when you ask for a mandate. If it's only at onboarding for the monthly fee, everything you bill on top starts outside it. One mandate covers varying amounts, so the same mandate can collect your project invoice or annual renewal, as long as your customer gets advance notice of each amount.
You're most likely to get a mandate signed while the price is being agreed. Adfin integrates with the proposal tool Socket, so your customer can sign the mandate as they accept the proposal or engagement letter. They're then notified at least three working days before each collection.
Cost matters more on big amounts. On Adfin a direct debit costs 1% + 20p, with the percentage capped at £4 and an extra 0.3% on amounts above £2,000, so a £4,000 direct debit costs you less than £20. The same invoice paid by business card at 2% + 20p costs £80.20. For the invoices that still go out on demand, its collection agents chase over email, SMS and WhatsApp within rules you set.
Common questions
Do bigger invoices get paid later? A little, when customers choose when to pay: 41.3% of invoices of £2,500 or more were late against 30.4% under £100. But the typical delay was eight days at every size, and much of the gap reflects which businesses issue large invoices.
Does direct debit work less well on large invoices? No. In Adfin's data direct debit collected 94.5% to 95.5% of requests in every size band, and the largest band had the fewest failed attempts.
Why are large invoices less likely to have a mandate? Mandates tend to be set up for recurring fees, large one-off invoices are more often under discussion, and some finance teams prefer to approve big payments themselves.
Can one direct debit mandate collect different amounts? Yes. The amount can vary from one collection to the next under the same mandate, as long as the customer gets advance notice.
How much does a large direct debit cost on Adfin? 1% + 20p with the percentage capped at £4, plus 0.3% on amounts above £2,000. A £4,000 direct debit costs less than £20.
How can I get more customers onto direct debit? Ask for the mandate while the work is being agreed, ideally alongside the proposal or engagement letter, and check coverage on your largest invoices, not just your monthly fees.
Sources
- Adfin - Pricing (accurate as of October 2026) https://www.adfin.com/pricing
- Adfin - Next-generation direct debit (accurate as of October 2026) https://www.adfin.com/direct-debit-payments
- Bacs - The Direct Debit Guarantee (accurate as of October 2026) https://www.bacs.co.uk/directdebit/directdebitguarantee
- Adfin - Credit control (accurate as of October 2026) https://www.adfin.com/credit-control
