ABA
The ABA file is how an Australian organisation actually pays anyone at volume — a fixed-width text file, lodged with the bank, that moves money out the door. It is the last step of Procure-to-Pay and of payroll, and the point at which a configuration error becomes a real payment to a real stranger.
Data in and out
- IN Payment file from Accounts Payable · per payment run
- IN Net pay file from Payroll · per pay run
If you change this
It implies 7 topics across 2 modules, including Supply Chain Management which you might not expect.
See the path ahead →Why it matters
The format is unglamorous and the stakes are not. An ABA file is the instruction to move money; once the bank accepts it, recovery depends on the goodwill of whoever received the funds.
- It is the fraud surface: Invoice fraud rarely defeats the matching engine. It changes the bank account on a legitimate supplier and lets the file pay it correctly.
- It is unforgiving: Fixed-width, positionally parsed. A misplaced character shifts every field after it.
- It is bank-specific: The standard is a convention rather than a specification, and each bank varies it.
- It is the point of no return: Approval workflow is reversible. A lodged file is not.
What the file is
The Australian Bankers Association format — universally called ABA, sometimes Direct Entry or Cemtex — is a plain text file of fixed-width records.
- 01
Descriptive record
One line per file. Names the originating organisation, the user identification number issued by the bank, and the processing date.
- 02
Detail records
One line per payment. BSB, account number, amount in cents, account title, lodgement reference, and the trace record for the debit side.
- 03
Total record
One line per file. Net, credit and debit totals, and the count of detail records. The bank rejects the file if these do not reconcile.
Amounts are in cents with no decimal point, right-justified and zero-filled. A dollar value that reaches the file with a decimal point becomes a payment a hundred times too large or too small.
What you need in place
- Vendor master control: Creating or amending bank details is the highest-risk transaction in the finance system. It needs dual authorisation and callback verification against a number you already held.
- BSB validation: Checked against the current BSB directory, not just for length. BSBs are retired and reissued.
- A user identification number: Issued by your bank, specific to the account the file debits. It is not interchangeable between banks.
- Balanced or unbalanced convention: Some banks require a matching debit trace record, some do not. Getting this wrong produces silent rejection.
- Segregation of duties: Whoever creates the file cannot be the person who lodges it.
- A retained copy: The exact file lodged, kept as evidence, because the bank's copy is the one that will be cited in a dispute.
Where it goes wrong
01Bank variation
Have we tested against this bank's ABA specification, not a generic one?
Get the bank's own documentation and test a file end to end before go-live, including a rejection case.
02Vendor master
Who can change a supplier's BSB and account number, and who checks?
Dual authorisation with callback verification to a number already on file. Not the number on the invoice.
03File handling
Where does the file sit between generation and lodgement?
A file written to a shared drive is editable by anyone with access. Generate straight into the banking channel.
04Duplicate lodgement
What stops the same file being lodged twice?
Sequence numbering and reconciliation against the bank statement the next day.
05Remittance
How do suppliers know what was paid?
Remittance advice from the same run that produced the file, not a separate manual process.
Metrics and KPIs to track
File rejection rate
Files rejected by the bank, and the reason for each.
Payment run cycle time
Elapsed time from approved payment proposal to funds released.
Vendor bank detail changes
Count per period, with the proportion verified by callback.
Duplicate payment value
Value of duplicates detected, and of those recovered after payment.
Unreconciled payments
Payments in the file not matched to a bank statement line.
Australian specifics
- The format predates modern payment rails and persists because it is universally accepted by Australian banks.
- The **New Payments Platform** and PayTo are steadily taking volume, particularly for real-time and consumer payments, but ABA remains the default for bulk supplier and payroll disbursement.
- **Superannuation** contributions use SuperStream rather than ABA — a separate obligation with its own format and gateway.
- Lodgement cut-off times are bank-specific and shift around public holidays. A payment run scheduled without reference to the Victorian public holiday calendar will sit unprocessed.
Alongside this