BACS payments for payroll providers

The three-day cycle is the whole constraint

BACS Direct Credit — the scheme most UK salaries are paid over — settles on a fixed three-working-day cycle. There is no expedited option and no way to compress it:

Weekends and bank holidays are not working days, and BACS follows the England and Wales calendar. That last detail matters for Scottish bureaus: 2 January is a bank holiday in Scotland but an ordinary BACS processing day — except in the years when 1 January falls at a weekend and 2 January becomes a substitute holiday in England and Wales too. The reverse applies to holidays observed only in England and Wales. Check the year you are planning against the Bacs processing calendar rather than assuming.

Scheduling backwards from payday

Work the calendar in reverse, and build slack in deliberately rather than discovering you need it:

1. Fix payday, then count back two working days

   That is your submission date. A Monday payday means a Thursday submission. A payday the day after a bank holiday moves the submission back a further day, which is where December runs go wrong.

2. Count back again for your own cut-off

   Your provider or sponsor has a cut-off time on submission day, and it is usually well before the end of the working day. Treat that as your real deadline, and give yourself at least a few hours of margin for a rejected file.

3. Set the client data deadline earlier still

   The failure mode that dominates in practice is not a technical one: it is a client sending late or amended payroll data. A bureau that sets its client deadline the day before its own submission cut-off absorbs that without drama; one that sets it the same morning does not.

4. Publish the December calendar in November

   Christmas and New Year compress several runs into fewer working days, and it is the one time of year clients reliably ask. Sending the dates before they ask is cheap and buys a lot of goodwill.

Your own Service User Number, or someone else's

To submit to Bacs you need a Service User Number. A bureau has two routes to one, and the choice is more consequential than it first looks.

The point most often underweighted is the cut-off. Submitting through an intermediary means inheriting their deadline, which is necessarily earlier than the scheme's. For a bureau whose clients habitually send data late, an hour of lost submission window is a recurring operational cost rather than a one-off inconvenience.

The full mechanics of SUN sponsorship, and the collection side of Bacs, are covered in our Direct Debit guide and the general BACS payments guide.

Standard 18 files, and the field that matters

Bacs instructions are submitted as Standard 18, a fixed-width format carrying the destination sort code and account number, the amount, a transaction code and a reference. Most payroll software exports it directly, so the format itself is rarely the problem.

The reference field is. It is what the employee sees on their bank statement, and for a bureau paying on behalf of many employers it is the difference between an employee recognising their salary and ringing someone to ask what the payment is. Use the client employer's trading name, not the bureau's, and not an internal run identifier. This sounds trivial and generates a surprising share of avoidable client contact.

Two checks worth automating on file build: that no line has a zero or negative amount, and that the sort code and account number pass a structural check. Neither is exotic, and both catch errors that are expensive after day three.

Client fund segregation at scale

A bureau paying twenty client employers from a single pooled balance faces a reconciliation problem that grows faster than the client list. When money arrives from a client, it has to be matched. When a payment fails and returns, it has to be attributed. When a client asks what happened to their funds on a given date, the answer has to be exact.

The structural answer is one virtual IBAN per client employer. Funds arrive already attributed, because the account they arrived into identifies the client. Returns are unambiguous. And a client query is answered by looking at their account rather than by reconstructing a pooled ledger.

This matters more than it used to, because the alternative — opening a separate bank account per client — is slow and expensive at any scale worth having. A bureau with forty clients is not going to run forty high-street accounts.

If any of those clients pay staff in euro, the same segregation applies but the settlement calendar does not: see our companion guide to SEPA payments for payroll providers.

When a run misses its window

It happens. The question is what you do in the hour after you notice, and the options are all more expensive than having been on time.

Faster Payments is the practical answer for a handful of affected employees. It runs at weekends, which BACS does not, so a Friday discovery does not have to wait for Monday. The cost per payment is negligible next to the cost of an unpaid employee.

What makes this manageable is having the alternative rails available from the same balance you were going to pay from. A bureau that has to move money to a different provider before it can send a Faster Payment has lost the time it was trying to save.

The recall window nobody uses

The flip side of the three-day cycle is genuinely useful and often forgotten: a file submitted on day one has not credited anyone yet. If you spot an error — a wrong amount, a leaver still in the file — the run can normally be withdrawn or replaced up to your submission cut-off on the input day. After that the file is in the scheme, and withdrawing it depends on your sponsor or provider rather than being something you can simply do. Instant rails give you no window at all. It is worth knowing your provider's exact process and deadline for this before the afternoon you need it.

Frequently asked questions

How far in advance does a BACS payroll file need to be submitted?

BACS runs on a three-working-day cycle: the file is submitted on day one, processed on day two, and credited to employees on day three. So a file must be submitted two working days before payday. Weekends and bank holidays are not working days, which means a Monday payday needs the file in on the preceding Thursday, and a bank holiday pushes everything back a further day.

Does a payroll bureau need its own Service User Number?

Not necessarily. A bureau can submit through a facilities management provider or a sponsor that already holds a Service User Number, which avoids the sponsoring bank's credit assessment and is faster to start. Holding your own SUN means your own name appears against the payment and you control the submission process, which becomes worth the approval process as volumes grow.

What is a Standard 18 file?

Standard 18 is the fixed-width file format Bacs uses for payment instructions. Each record carries the destination sort code and account number, the amount, a transaction code identifying the payment type, and a reference. Most payroll software exports it directly, and the practical risk is not the format itself but what goes in the reference field, which is what the employee sees on their statement.

Can a BACS payroll payment be recalled after submission?

There is a window, but it is shorter than the three-day cycle suggests. In practice it runs until your submission cut-off on the input day: up to that point a file can normally be withdrawn or replaced. After the cut-off, withdrawing it depends on your sponsor or provider and is not guaranteed. Once funds have credited on day three, recovery depends on the recipient agreeing to return them. Even so, that window is more than an instant rail gives you, which is one reason scheduled payroll runs on BACS.

What happens if a payroll bureau misses the BACS submission deadline?

The run moves to the next cycle, which means employees are paid a working day late. The usual remedies are to pay affected employees by Faster Payments, which is near-immediate but subject to value limits, or CHAPS for larger amounts on the same working day. Both cost more per payment than BACS, which is why the submission deadline is the deadline that matters in a bureau's calendar.

Written by the financeb2b editorial team · Scheme facts sourced from Bacs and Pay.UK scheme documentation · Last updated 31 August 2026 · Editorial policy