Bacs and Direct Debit FAQs
Straight answers to the questions UK businesses ask us most about Bacs, Direct Debit, Service User Numbers and choosing between software and a bureau. Each answer links to the page that covers it in full.
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GETTING STARTED
What is Bacs?
Bacs is the UK scheme that moves money directly between bank accounts, by Direct Debit (collecting money) and Direct Credit (paying it out, for example salaries and suppliers). It is run by Pay.UK. Businesses submit payment files to Bacs through approved software or an approved bureau.
What is the Bacs three-day cycle?
A Bacs submission takes three working days: input day (the file is submitted), processing day (Bacs processes it) and entry day (money leaves or reaches the account).
What is the difference between a Direct Debit and a Direct Credit?
A Direct Debit collects money from a payer's account with their authority (a mandate). A Direct Credit pays money into an account, such as salaries, pensions or supplier payments.
What does Bacs approved mean?
SOFTWARE OR BUREAU?
Should we use Bacs software or a Bacs approved bureau?
It comes down to one question: do you have the internal resource to run Bacs submissions? If yes, Bacs approved software gives you control. If not, a Bacs approved bureau submits for you. Interbacs supplies both.
What does a Bacs approved bureau do?
A bureau submits your payment files to Bacs on your behalf, under your own Service User Number, and handles the submission process for you. See what is a Bacs approved bureau?
Can we switch from a bureau to our own software later?
Yes. Businesses move to their own software as volumes grow, and back to a bureau when a team shrinks. Your mandates move with you. The Solution Finder can help you decide where to start.
SERVICE USER NUMBERS
What is a Service User Number (SUN)?
A Service User Number is the unique six-digit number that identifies your business to Bacs. Every Direct Debit you collect and every Direct Credit you pay carries it.
Do we need our own SUN to use a bureau?
Yes. A Bacs approved bureau submits under your Service User Number; it does not lend you one. You need your own SUN whether you use software or a bureau.
How do we get a Service User Number?
You apply through a sponsoring bank, which assesses your trading history, financial standing and how you plan to use the scheme. See am I eligible for a Service User Number?
What changes for Non-AUDDIS SUNs in 2027?
SUBMITTING TO BACS
What is Bacstel-IP?
Bacstel-IP is the secure channel every Bacs submission travels over. Software builds the payment file, signs it with a digital certificate and transmits it. See what is Bacstel-IP software?
What is a Hardware Security Module (HSM)?
An HSM holds your Bacstel-IP signing certificate in tamper-resistant hardware, so submissions can be signed and sent automatically without a smart card. See Hardware Security Modules.
What are ARUDD and ADDACS reports?
They are Bacs reports returned after collection. ARUDD tells you which Direct Debits were unpaid and why; ADDACS tells you which mandates a payer has changed or cancelled. Acting on them promptly is a scheme requirement.
What is AUDDIS?
DIRECT DEBIT RULES
What is the Direct Debit Guarantee?
It protects payers: if a payment is taken in error, the payer is entitled to an immediate refund from their bank. Every business collecting by Direct Debit must offer it.
What is advance notice?
Before collecting, you must tell the payer the amount and date. The standard period is 10 working days, unless you have agreed a different period with the payer.
What is an indemnity claim?
When a payer claims a refund under the Direct Debit Guarantee, their bank reclaims the money from you through an indemnity claim.
WORKING WITH INTERBACS
How long has Interbacs been supplying Bacs services?
Since 2003. Interbacs is a Bacs approved software supplier and a Bacs approved bureau, certified to ISO 9001 and ISO 27001.
Can we see the software before we commit?
Yes. Book a free demo and our team will walk you through it, built around your own collection schedule.
How easy is it to switch bureau supplier?
We work with you to ensure the process is seamless. From start to finish, we take care of it to ensure no disruption. Read our in-depth 3-Step Switch Solution guide that goes into more detail.
Still have a question?
Talk to a Bacs specialist. No hard sell – just a straight answer about your collections or payments.