Understanding AUDDIS, ADDACS and ARRUD Reason Codes
If you work with UK Direct Debits, you will eventually encounter three acronyms: AUDDIS, ADDACS, and ARRUD. Each represents a distinct Bacs messaging service, and each carries its own set of reason codes that tell you exactly why something happened — and what you need to do next.
What are Bacs Payment Services?
Bacs (Bankers' Automated Clearing Services) is the UK scheme that powers Direct Debit and Bacs Direct Credit. Originators — companies that collect Direct Debits — submit files to Bacs via a service bureau or direct submission. Banks process those files and respond with structured notification files: AUDDIS, ADDACS, and ARRUD are three of the most important response types.
Understanding these messages is critical. Ignoring them — or mishandling their reason codes — leads to collection failures, cancelled instructions, and payer complaints.
AUDDIS — Automated Direct Debit Instruction Service
AUDDIS lets originators submit new Direct Debit Instructions (DDIs) electronically to the payer's bank, rather than relying on paper mandates. The bank validates the instruction and responds with an AUDDIS notification.
Why you receive AUDDIS messages
You receive an AUDDIS response when a bank accepts or rejects a new DDI you submitted. A rejection carries a reason code that tells you what went wrong.
AUDDIS reason codes
| Code | Meaning | Recommended action |
|---|---|---|
| 1 | Instruction cancelled — refer to payer | Contact the payer; do not re-submit without a new mandate |
| 2 | Payer deceased | Cancel the instruction immediately |
| 3 | Account transferred to a different bank or branch | Contact payer for new account details |
| 5 | No account (account number not found) | Verify account details with the payer |
| 6 | No instruction found | Check your submission; the DDI may not have been received |
| B | Account closed | Contact payer for new account details |
| C | Account transferred to a different branch of the same bank | Update sort code; new details should arrive via ADDACS |
| F | Invalid account type (e.g. savings accounts that do not accept DDs) | Contact payer for a valid current account |
| I | Payer reference not unique | Ensure your service user number / reference combination is unique |
| K | Instruction cancelled — please re-present | Re-submit the DDI |
| L | Incorrect payer's account details | Verify account number and sort code with the payer |
| N | Transitional error | Re-submit; this is a processing error, not a permanent rejection |
| O | Invalid reference | Check the payer reference format against Bacs rules |
| R | Instruction re-instated | No action required; the DDI is active again |
| S | Duplicate instruction — new instruction and existing instruction found | Investigate; you may be submitting against an already-active DDI |
ADDACS — Automated Direct Debit Amendment and Cancellation Service
Where AUDDIS is about new instructions, ADDACS is about changes to existing ones. Banks send ADDACS messages when a payer changes bank account, closes an account, or cancels a Direct Debit.
Why you receive ADDACS messages
You receive ADDACS notifications when your payer's bank makes a change to a live DDI — usually because the payer has contacted the bank directly to cancel or amend the instruction.
ADDACS reason codes
| Code | Meaning | Recommended action |
|---|---|---|
| 0 | Instruction cancelled — bank will advise payer | Cancel the DDI from your records |
| 1 | Instruction cancelled — refer to payer | Cancel the DDI; contact the payer |
| 2 | Payer deceased | Cancel the DDI immediately |
| 3 | Account transferred to a different bank or branch | Contact payer for new account details; re-submit DDI |
| B | Account closed | Contact payer for new account details |
| C | Account transferred to a different branch of the same bank | Update the DDI with the new sort code provided in the record |
| D | Advance notice disputed | The payer is disputing your advance notice; contact them |
| E | Instruction amended — new account details in record | Update your records with the new account details from the ADDACS record |
| R | Instruction re-instated | The DDI has been re-activated; resume collections if appropriate |
ARRUD — Automated Return of Unapplied Direct Debits
ARRUD messages are returned when a Direct Debit collection cannot be applied to the payer's account. Unlike AUDDIS (which covers new instructions) and ADDACS (which covers amendments), ARRUD is about failed collections.
Why you receive ARRUD messages
When you submit a Direct Debit collection and the bank cannot process it, the collection is returned via ARRUD. This is sometimes called an "unpaid" Direct Debit.
ARRUD reason codes
| Code | Meaning | Recommended action |
|---|---|---|
| 0 | Refer to payer | Contact the payer — the bank has not given a specific reason |
| 1 | Instruction cancelled — refer to payer | Do not re-present; contact payer and obtain a new mandate |
| 2 | Payer deceased | Cancel the DDI; do not re-present |
| 3 | Account transferred to a different bank or branch | Contact payer for new account details |
| B | Account closed | Contact payer for new account details; cancel existing DDI |
| C | Account transferred to a different branch of the same bank | Update sort code from the corresponding ADDACS C notification |
| E | Instruction amended — new account details in record | Use the new account details provided; update your records |
Common Gotchas
Don't re-present after a code 1. Reason code 1 across all three services means the payer has explicitly cancelled. Re-presenting will result in an indemnity claim under the Direct Debit Guarantee.
ADDACS C and ARRUD C go together. When a payer switches branches, you will typically receive an ADDACS C with the new sort code, followed by an ARRUD C if you attempted a collection before updating your records. Always process ADDACS before submitting collections.
ARRUD 0 is not an excuse to keep trying. "Refer to payer" means the bank couldn't honour the collection but hasn't told you why. Contact the payer before re-presenting; repeated failures can lead to your service user number being suspended.
Timestamps matter. Bacs processing operates on a three-day cycle. AUDDIS responses arrive on Day 2; ADDACS and ARRUD arrive throughout the cycle. Build your processing pipeline to handle these in order.
Log every reason code. Regulators and auditors want to see that you acted appropriately on every notification. Store reason codes against each DDI and collection record, and document the action taken.