You can edit an ABA file, but it is not an ordinary document. Every record is fixed width, so adding or removing a character in one field can shift the remaining fields and make the entire line invalid. The safest approach is to use an ABA-aware editor that exposes labelled fields and rebuilds the fixed-width records for you.
Before you edit the file
Make a backup of the original and work on a copy. If the file came from payroll or accounting software, consider correcting the source data and exporting it again. That keeps the payment file consistent with the system that produced it and creates a clearer audit trail.
This is also the workflow recommended by Westpac when an ABA import fails: review the failure details, fix the problem in the accounting software, and import the file again. MYOB's official guidance similarly explains how to reopen the relevant electronic transaction and recreate the bank file.
Manual editing is more appropriate when you understand why the file is wrong and the source cannot be regenerated in time. Follow your organisation's payment approval, access-control, and record-retention procedures.
1. Diagnose the problem first
If a bank rejected the file, read the rejection message before changing anything. A validator can then identify structural and field-level problems, such as an invalid BSB, a field that is too long, or totals that do not match the payment rows.
A format validator cannot confirm whether an otherwise valid account number belongs to the intended recipient. Verify payment instructions against an approved source rather than relying only on syntax checks.
2. Open the file in an ABA editor
Upload the working copy to the editor. Review the file header, transaction records, and control totals. Locate the record identified by the validator or bank message.
Typical corrections include:
- changing an incorrect BSB or account number;
- correcting an amount;
- shortening an overlong account title or lodgement reference;
- updating the requested processing date;
- correcting the Direct Entry user or trace details; and
- adding or removing a payment row.
Treat changes to destination accounts and amounts as high risk. Use your normal independent verification and approval process before saving them.
3. Preserve the ABA field rules
An ABA-aware editor should enforce field widths and rebuild the records, but the values still need to be appropriate:
- retain leading zeroes in BSBs and account numbers;
- use valid transaction codes;
- keep names and references within their permitted lengths;
- avoid unsupported characters;
- enter amounts in the units expected by the editor; and
- use the bank-issued originator and trace details.
When a payment is added, removed, or its amount changes, the file total record must also change. Do not manually guess the control totals; let the editor recalculate them from the payment records.
4. Download a new copy
Save the corrected file under a new, recognisable filename rather than overwriting the original. This makes it easier to compare versions and retain evidence of what changed.
Do not open and resave the corrected output in Excel or a rich-text editor. Those programs can alter spacing, quote values, convert numbers, or change line endings.
5. Validate after editing
Every material edit should be followed by another validation. Confirm that:
- each record has the expected structure;
- mandatory fields are present;
- BSBs and transaction codes have valid formats;
- the transaction count is correct;
- debit and credit totals reconcile; and
- the net total matches the detail records.
Then inspect the corrected file and compare the payments with the approved source data.
Can I edit an ABA file in Notepad or TextEdit?
Technically yes, because ABA is plain text. It is risky because field boundaries are invisible and ordinary editors do not automatically recalculate totals. A single inserted character can invalidate a record even when the text looks reasonable.
If you must use a text editor, work on a copy, use a monospaced font, disable word wrapping, preserve the existing encoding and line endings, and validate the result. An ABA-specific editor is safer for most changes.
Can I edit an ABA file in Excel?
Excel is useful for editing the source payment data, but it should not directly edit the fixed-width ABA output. Convert the ABA to a spreadsheet for analysis, or correct the original workbook and generate a fresh ABA file.
Final checklist
Before uploading the edited file to a bank:
- Retain the untouched original.
- Document why the change was required.
- Independently verify account and amount changes.
- Validate the new file.
- Compare the payment count and total with the approved batch.
- Follow the bank's normal upload and dual-authorisation process.
