Moving a client base onto direct debit runs one of two ways. Where enough mandates are moving from another provider, the Bacs Direct Debit Bulk Change Process moves them across and your clients sign nothing. Below your provider's threshold, each client signs a new one. Both routes need at least three working days' notice, and neither leaves a gap in your collections.
In this article
The short version
- Where enough mandates are moving, the Bacs Direct Debit Bulk Change Process moves the instructions and your clients don't re-sign.
- Below your provider's threshold, each client signs a new mandate, and you skip the bulk change paperwork entirely.
- No Bacs document publishes a minimum number of mandates for a bulk change, so any figure you're quoted is your provider's own policy. Ask them.
- Three or more working days' notice before the change date, with collections continuing through it.
- Across the providers clients have moved from, the median time from the agreed change date to mandates being active is three to five days (Adfin platform data).
- When Cloud Accounting Support Services moved more than 200 clients, 89% signed their new mandate within three days (Adfin platform data).
- The mandate authorises your client's bank, not you, so the paperwork has to be right before anything is lodged.
The two routes, and which one you get
The size of your book decides the method, and where the line falls is your provider's decision. No Bacs document publishes a minimum number of mandates for a bulk change, and nor does GoCardless, Stripe, London & Zurich or Access PaySuite, so ask your incoming provider what their threshold is and treat the answer as commercial policy.
| Route | When it applies | What your client does | What happens underneath |
|---|---|---|---|
| Bulk change | Enough existing mandates with another provider to meet your provider's threshold | Nothing, beyond reading your notice | The instructions transfer under the Bacs Direct Debit Bulk Change Process |
| Re-sign | Below that threshold, or clients not on direct debit yet | Signs a new mandate | The new instruction is lodged with their bank in the usual way |
Both are legitimate and both are used every week, so if a provider offers you only one of them, ask why. The bulk change is the gentler experience for your clients because nobody has to do anything, and it carries more paperwork on your side. Re-signing puts a small ask in front of every client, and it's quicker to start, since there's no bulk change to wait on.
There's a second reason the count matters. Under the re-sign route you find out fairly quickly who's still engaged with you, because the clients who don't sign are the ones you'd probably have chased anyway.
What to get straight before you pick a change date
Four things tend to hold up a migration, and all of them are easier to sort out now than halfway through.
- Your client list has to match your mandate list. Old mandates for clients who left, duplicates under two spellings of the same company name, mandates for fees you no longer charge: clean these up first, because a bulk change moves whatever you give it.
- Your collection schedule needs rebuilding on the new side. The mandate is only the authority to collect. The amounts, the dates and the invoices sit in your system, and they don't travel with the instruction.
- The deed and the timetable, on the bulk change route. Moving mandates away from GoCardless, for example, involves a Bacs bulk change with a wet-signed deed and around four to six weeks, with schedules rebuilt on the other side (verify at the time, since providers update this). Other major UK direct debit providers run a comparable process.
- Someone has to own the notice to clients. Not the provider, you. Your clients recognise your name on a bank statement and your voice in an email, so the message lands better coming from you.
If you're moving fee collection and your engagement letters at the same time, do them in that order: get the migration finished, then change what you're collecting.
What the timeline looks like in practice
Three separate waits run here, and people usually merge them into one and then worry about the wrong part.
The paperwork wait comes first on the bulk change route, and your two providers mostly handle it between themselves. Your change date is the second, chosen by you and announced to clients at least three working days beforehand. Then everything from that date onwards.
That last stretch is measurable. Across the providers clients have moved from, the median time from the agreed change date to mandates being active is three to five days (Adfin platform data). So the part clients experience as "the switch" is usually shorter than the week they were braced for.
On the re-sign route the wait that matters is a human one. When Cloud Accounting Support Services moved more than 200 clients across, 89% signed their new mandate within three days (Adfin platform data). The remaining few are the whole job, and chasing them is what decides whether your migration takes a week or a month. Adfin chases unsigned mandates automatically for that reason.
Collections carry on throughout. The point of giving notice and setting a change date is that no invoice falls into a hole between the old provider and the new one, and if anyone tells you a migration means pausing collection for a cycle, that's a description of their process rather than a scheme rule.
Clients who aren't on direct debit yet
Most practices moving a client base are doing both jobs at once: shifting the clients already on direct debit, and putting the rest onto it for the first time. The second group is the bigger prize and the slower work, because every one of them signs.
A few things make it go faster. Tie the ask to something already happening, such as a renewal, a fee review or the annual engagement letter, so the mandate arrives with a reason attached instead of on its own. Send it to the person who actually signs, not to an info@ address. And say what you're collecting and when, because a client who knows the amount and the date has nothing left to think about.
Paperless mandates are what make this practical, and they come with conditions. Bacs says paperless direct debit "enables organisations to sign up customers for Direct Debit collections for example over the telephone, Internet, telephone keypad, face-to-face or by interactive TV", that it's "only available to organisations using the AUDDIS service and who can satisfy additional criteria", and that "it is the organisation's responsibility to verify the customer and validate their details". Confirmation goes to the customer within three working days of their verbal or internet instruction. Collecting under a provider's Service User Number means the provider holds that compliance, and the verification duty still touches you.
Telling clients, and what they tend to ask
The notice is short. What's changing, when, what the amount and date will be, what they need to do, and who to reply to. Our guide on how to tell clients you're moving them to direct debit covers the wording and the client who says no.
Two questions come up almost every time. Clients ask whether their protection changes, and it doesn't: the Direct Debit Guarantee is offered by every bank and building society that accepts direct debit instructions, and it entitles a payer to "a full and immediate refund" from their own bank if an error is made in the payment. They also ask whether you can now take what you like, and the answer is in the definition: a direct debit lets you collect varying amounts "as long as the customer has been given advance notice of the collection amounts and dates".
Say both of those in your own words in the first email and you'll answer most of the replies before they're sent.
The first month after the change
Watch three things once collections are running again.
Mandates that never went active are the first. On the bulk change route a small number tend to fall out because the account has closed or moved bank since the instruction was set up, and you'll hear about those through the bank messages your provider passes on. Treat them as a short re-sign list.
Failed first collections are the second, and they're rarely dramatic. A first collection under a new arrangement can fail because the client moved money out on the same date they always did. Retry, and if you have card fallback, use it.
Your own reconciliation is the third. Payments now arrive on a different rhythm, three working days after submission through the Bacs cycle, so the first month's bank reconciliation looks unfamiliar even when everything has worked. Check it once properly and you'll trust it afterwards.
Common questions
Do clients have to sign a new mandate when you change provider? Not if the bulk change route applies, because the Bacs Direct Debit Bulk Change Process transfers the existing instructions. Below your provider's threshold, each client signs a new mandate. No Bacs document publishes that threshold, so ask your provider.
How long does migrating a client base take? Across migrations onto Adfin, the median time from the agreed change date to mandates being active is three to five days. The bulk change paperwork before that date takes longer and is mostly handled between providers.
Will collections stop while we migrate? No. Notice of at least three working days goes out before the change date and collections continue through it, so there's no gap to plan around.
How much notice do clients need before the change? Three or more working days for the change itself. Where the amount, date or frequency of a payment changes, the Direct Debit Guarantee tells payers they'll be notified normally 10 working days in advance, or as otherwise agreed.
What proportion of clients sign a new mandate quickly? When Cloud Accounting Support Services moved more than 200 clients onto Adfin, 89% signed within three days. Chasing the rest is usually what sets the overall timeline.
Can you migrate clients who have never paid by direct debit? Yes, and they sign a mandate like any new one. Attaching the ask to a renewal or an engagement letter tends to get it signed faster than sending it on its own.
Sources
- Bacs — Direct Debit (accurate as of August 2026)
- Bacs — paperless Direct Debit (accurate as of August 2026)
- Direct Debit — the Direct Debit Guarantee (accurate as of August 2026)
This article explains how a direct debit migration works and is not legal or financial advice. The Bacs scheme rulebook is not publicly available, so anything not quoted from a scheme page is described as what providers publish. Last updated August 2026.
