Since 2003: One of the UK's first Bacs Solution Suppliers
Bacs Approved: Software and Bureau
ISO 27001: and ISO 9001 certified, ICO registered
Bacstel-IP: Submit straight to Bacs, no third party

GETTING STARTED

Submit straight to Bacs, without a third party

Bacs approved software lets your business submit Direct Debit and Direct Credit files straight to Bacs, without a third party in between. If you have the three things below, software is usually the cheaper route over time and gives you full control of your collection calendar.

Your own Service User Number

The unique six-digit number that identifies your business to Bacs. You apply through a sponsoring bank.

What is a SUN?

A sponsoring bank

Your bank assesses your trading history, financial standing and how you intend to use the scheme.

Someone to run submissions

A person in the business who can run submissions reliably to the Bacs three-day timetable.

SOFTWARE OR BUREAU?

Do you need Bacs software, or a Bacs Bureau?

The question turns on whether you have the internal resource to run Bacs submissions yourself. Software suits a business with its own Service User Number and somebody who owns the payment calendar. A Bacs approved bureau suits a business that has neither, or that would rather not build the capability for the volumes involved. More than half of all organisations using Bacs submit through an approved bureau rather than in-house.

	In House Bacs Software	Bacs Approved Bureau
Who submits to Bacs	Your team	Interbacs, from your file
Service User Number	Required	Required
Failed Payments	Your team	Your team or ours
Indemnity Claims	Your team	Your team or ours
Bacstel-IP connection	Your own certificate	Our certificate
Best suited to	Finance team with capacity	No internal expertise
Cost shape	Licence plus your time	Per transaction fee

You can switch later

Neither route is a permanent solution. Businesses move from a bureau to their own software as volumes grow and the team builds, and back the other way when a finance team shrinks or they wish to lighten the burden on them. Switching is a documented process rather than a rebuild, and your mandates move with you.

Interbacs supplies both. If a bureau sounds like the better fit, see our Bacs Approved Bureau page.

OUR SOFTWARE

What Bacs software does Interbacs supply?

InterPay is "file agnostic", meaning you can use payment files from any software. From standard manual uploads through to full automation and approval, it is a universal Bacs submission software.

InterPay

Bacs approved submission software. InterPay builds and submits Direct Debit and Direct Credit files over Bacstel-IP, handles the returned reports, and supports multiple Service User Numbers where a group collects for several trading entities. It is available on your own servers or hosted, and it is the product most Interbacs customers start with.

Explore InterPay

DDMS

Direct Debit Management Software. DDMS manages the mandates themselves: setting up new payers, applying advance notice, changing collection dates and amounts, tracking failures through to resolution, and reporting on the whole collection cycle. If InterPay is how the file reaches Bacs, DDMS is how you run the operation that produces it.

Explore DDMS

InterPass

Identity verification. InterPass checks that the person setting up a Direct Debit is who they say they are, and that the account they have given belongs to them. Paperless Direct Debit sign-up carries an obligation to verify, and InterPass meets it without adding a manual step to your sign-up flow.

Explore InterPass

HSM

Tamper-resistant signing. A hardware security module holds your Bacstel-IP signing certificate in tamper-resistant hardware rather than on a workstation. Larger submitters and businesses with formal security requirements generally want one; smaller submitters generally do not need one.

Explore HSM

SERVICE USER NUMBERS

What is a Service User Number, and do you need one?

A Service User Number, or SUN, is the unique six-digit number that identifies your business to Bacs when you pay or collect money through the scheme. Every Direct Debit you collect and every Direct Credit you pay carries it. You apply through a sponsoring bank, which assesses your trading history, financial standing and how you intend to use the scheme.

You need your own SUN for either route (software or a Bacs approved bureau). A bureau submits under your number; it does not lend you one. If a Service User Number is not available to you yet, Direct Debit facilities management is the arrangement that lets you collect under a provider's number instead, and we will introduce you to a specialist partner for that.

PLAN AHEAD FROM 1 JULY 2027

No new Non-AUDDIS Service User Numbers

Bacs has confirmed that from 1 July 2027, payment service providers will no longer create new Non-AUDDIS Service User Numbers. Any SUN created after that date will only be able to lodge instructions using AUDDIS. If you already hold a Non-AUDDIS SUN, nothing stops working, but a business planning a second SUN for a new trading entity should plan for it to be AUDDIS.

Read the full update

What does Bacs approval mean?

Interbacs has supplied Bacs software since 2003 and was one of the first Bacs Solution Suppliers in the UK. Approval is not a one-off: it is re-tested as the scheme changes, and a supplier that stops meeting the requirement comes off the register.

On the Pay.UK register, our Bacs Arpproved Software covers:

Bacs Approved Software: DDMS, DDMS Web, Interpay, Interpay Web and Hardware Security Module
Bacs Approved Bureau: DDMS, DDMS Web, Interpay, Interpay Web and Hardware Security Module
Bacs Electronic Elements Affiliate
ISO 9001:2015 and ISO 27001:2022 certified, registered with the ICO, and Cyber Essentials assessed

How do Bacs submissions reach the bank?

Through Bacstel-IP, the secure channel every Bacs submission travels over. Your software builds the payment file, signs it with a digital certificate held either in software or on a hardware security module, and transmits it. The three-day cycle then runs: input day, processing day, entry day.

ARUDD: Automated Return of Unpaid Direct Debits; telling you which collections failed and why.
ADDACS: Automated Direct Debit Amendment and Cancellation Service; telling you which mandates a payer has changed or cancelled.
AUDDIS: Automated Direct Debit Instruction Service; used to lodge new Direct Debit Instructions electronically.
AWACS: Advice of Wrong Account for Automated Credits; a Direct Debit went to an account that has since changed.