Agree the retainer amount, the collection date and the notice period in your terms, ask the client to sign a SEPA direct debit mandate, then send each month's invoice early enough to act as the notice of the collection. The money is taken on the same date every month, and any extra work goes on the next invoice so the client sees the full amount first. Through Adfin, a direct debit of up to €2,000 costs at most €2.20, with no monthly fee.
In this article
The short version
- Put the amount, collection date and notice period in your terms.
- The client signs a SEPA mandate once to cover every collection.
- The monthly invoice can double as the notice of collection.
- A €1,490 direct debit costs €2.20 through Adfin.
- A failed collection can be paid by payment link instead.
Set the terms before the first collection
Say you're a marketing consultant starting a retainer with a new client at €950 a month, including VAT, billed in advance, with extra hours at €90 including VAT. Before anything is collected, put four things in the engagement letter or terms the client signs.
- The amount and what it covers, and how extra hours are charged.
- The collection date, such as the 1st of each month, so the client can plan around it.
- The notice period. The SEPA rules require notice at least 14 calendar days before each collection unless you and the client agree a different timeline, so if you'd like to invoice on the 22nd for a collection on the 1st, write a seven-day notice period into the terms.
- That payment is by SEPA direct debit, with a fallback such as a payment link if a collection doesn't go through.
Agreeing the shorter period at the start saves trouble later, because without it the invoice would need to go out a fortnight ahead, before you know how many extra hours the month will bring.
Get the mandate signed and take the first month
The client signs a mandate once, and it covers every collection after that. Each collection also carries a creditor identifier: your own if you collect through your bank, which issues it, or your provider's, depending on how the provider works, so ask which applies.
Timing can mean the first month can't be collected by direct debit. If the retainer starts on 1 February 2027 and the mandate is only signed on 28 January, there isn't time to give seven days' notice. One way round it is to send the first month as a payment link by email, SMS or WhatsApp, which the client can pay by card, Apple Pay, Google Pay or bank transfer, and start direct debit from March. These are two separate steps, one after the other.
Each month: invoice, notice, collection
Here's how March runs for the consultant, with six extra hours worked in February.
- Monday 22 February: the invoice goes out for €1,490, the €950 retainer plus six hours at €90 (€540). It states that €1,490 will be collected by SEPA direct debit on Monday 1 March, which gives the client their notice.
- Friday 26 February: the collection is sent to the client's bank, which needs it at least one business day before the due date. A provider handles this for you.
- Monday 1 March: €1,490 leaves the client's account.
With Adfin, that collection costs €2.20. The 1% part, which would be €14.90, is capped at €2 on direct debit and bank transfer, and 20c is added. The same €1,490 paid by standard card would cost €15.10, because cards aren't capped. Over a year of plain €950 months, the direct debits come to €26.40 against €116.40 at the standard card price.
If you use Xero or QuickBooks, Adfin is a certified app for both with two-way sync, so each invoice is marked paid automatically when its collection goes through, and nobody has to match the retainer by hand.
If a collection fails or the retainer changes
A collection can come back if the client's account doesn't have enough in it or has been closed. You won't receive that month's money, so contact the client straight away and send a payment link for the amount while you sort out the cause.
The client can also ask their bank for a refund of any collection within eight weeks of the debit date, with no questions asked. A refund like that may point to a disagreement about the invoice, so talk to the client before collecting again.
When the retainer changes, say to €1,100 from June, tell the client in writing and let the next invoice carry the new amount with the usual notice. If a retainer pauses for a long time, keep in mind that a mandate with no collection for 36 months lapses, and the client would need to sign a new one.
Common questions
How much notice does a retainer client need before a direct debit? At least 14 calendar days before each collection, unless you and the client agree a different period. You can agree a shorter period in the terms so the monthly invoice can serve as the notice.
Can the monthly invoice be the direct debit notice? Yes, the SEPA rules allow the pre-notification to go out with another document, such as the invoice, as long as it's sent in time.
What does it cost to collect a €950 retainer by direct debit? With Adfin it's €2.20: 1% of €950 is €9.50, but on direct debit and bank transfer the 1% part is capped at €2, and 20c is added. Card payments aren't capped.
Can I start a retainer before the mandate is set up? You can take the first month by payment link, paid by card, Apple Pay, Google Pay or bank transfer, and start collecting by direct debit from the following month.
What happens if a retainer direct debit fails? You don't receive that month's payment, so contact the client and offer another way to pay, such as a payment link. Common causes are insufficient funds and closed accounts.
Can a client get a retainer payment back from their bank? Within eight weeks of the debit date, a client can get a refund of any authorised collection with no questions asked. After that, a refund is only possible if they claim the collection wasn't authorised, within 13 months.
Sources
- European Payments Council - 2025 SEPA Direct Debit Core Rulebook, version 1.0 (accurate as of November 2026) https://europeanpaymentscouncil.eu/sites/default/files/kb/file/2024-11/EPC016-06%202025%20SDD%20Core%20Rulebook%20version%201.0.pdf
- European Payments Council - Creditor Identifier Overview (accurate as of November 2026) https://www.oenb.at/dam/jcr:5193cd07-f090-4378-abcd-06d97c700ab2/EPC262-08-v12-0-Creditor-Identifier-Overview.pdf
- Citizens Information - Payment Services Directive (accurate as of November 2026) https://www.citizensinformation.ie/en/money-and-tax/personal-finance/eu-payments/psd2/
