Mistakes happen. Whether it’s a simple typo, missed income, or a forgotten GST credit, many Australian businesses find themselves needing to amend a previously lodged Business Activity Statement (BAS). The good news? In most cases, amending your BAS is straightforward, and you can usually do it online without penalties, provided you act promptly.
This guide walks you through everything you need to know to correct a BAS error. You’ll learn when you can make a correction versus when you need to request an amendment, how to do it through the ATO’s systems, and what to expect next.
Understanding the Difference: Corrections vs Amendments
What Is a BAS Correction?
A correction is a minor adjustment you can make in your next BAS. You’re allowed to correct mistakes from a previous period as long as the error falls within certain limits set by the ATO, both in dollar value and in time.
When to correct:
- The error relates to GST, fuel tax credits or wine equalisation tax.
- The amount falls under the ATO’s error value threshold (e.g., under $10,000).
- The mistake occurred within the past four years.
How to correct: Simply include the correction in the relevant field of your next BAS, usually under the “Adjustment” sections.
What Is a BAS Amendment?
An amendment is used when:
- The error exceeds the correction threshold.
- The error was made more than four years ago.
- You prefer to fix the error by revising the original BAS rather than including it in a later one.
How to amend: You’ll need to lodge a revised version of the original BAS for the relevant period, either online or through your tax agent.
Common Reasons for BAS Amendments
- Forgotten income or overstated sales
- Incorrect GST collected or GST credits claimed
- Missed fuel tax credits or wine equalisation tax entries
- Changes after receiving updated tax invoices
- Staff payroll errors impacting PAYG withholding
How to Amend a Previously Lodged BAS
Option 1: Amend Online via the Business Portal or Online Services
If you’re a sole trader or small business, this is the easiest method:
- Log into ATO Online Services for Business.
- Navigate to Lodgments > Activity Statements.
- Find the BAS you want to amend and select Revise.
- Make the necessary changes.
- Submit the amended BAS.
Note: Always keep records of the original BAS and your amended version.
Option 2: Using Your Registered Tax Agent
If you work with a tax or BAS agent, they can lodge the amendment on your behalf through their own ATO portal. This is especially helpful for complex changes or when errors span multiple BAS periods.
Option 3: Paper Amendment Form (Last Resort)
If online methods are not available, you can complete a paper Revision Request form (NAT 8552) and mail it to the ATO. However, this is the slowest method.
Time Limits for Amending a BAS
In most cases, the ATO allows you to amend your BAS within 4 years from the due date of the original lodgment. However, for fuel tax and wine equalisation tax, different rules may apply.
Acting early can help you avoid penalties or interest, especially if the amendment results in an underpayment.
Will I Be Penalised for Amending a BAS?
The ATO encourages voluntary disclosures. If you correct the BAS before the ATO contacts you about the issue, you may avoid penalties entirely.
You may still need to pay:
- Shortfall interest (if you owe money to the ATO)
- General interest charges (for late payments)
If the amendment results in a refund, the ATO may pay you interest on that amount, depending on how long it’s been since the BAS was first lodged.
What Happens After You Lodge an Amended BAS?
- You’ll receive a revised activity statement summary from the ATO.
- Any debit or credit adjustment will be reflected in your ATO account.
- If you owe money, you can pay through normal methods or arrange a payment plan.
- If you’re due a refund, the ATO will process it to your nominated account.
Tips to Avoid BAS Errors in Future
Use Accounting Software
Most cloud accounting platforms like Xero, MYOB, and QuickBooks automatically calculate GST, track PAYG, and even pre-fill your BAS. This reduces manual entry errors.
Reconcile Regularly
Do monthly reconciliations of your bank accounts, sales, and purchases. This helps pick up any missed transactions early.
Review Before Lodging
Double-check GST codes, payroll figures, and totals before submitting each BAS.
Work With a BAS Agent
A registered BAS or tax agent can save you from costly errors and ensure compliance.
Final Thoughts: Fixing BAS Mistakes Is Easier Than You Think
If you’ve made a mistake in your BAS, don’t panic. The ATO has designed flexible systems to help you correct or amend past lodgments, and most issues can be resolved quickly.
Whether you fix it in your next BAS or lodge a revision for the original, taking prompt action helps you stay compliant and reduces your risk of penalties.
If you’re unsure or if the error is substantial, it’s always a good idea to seek professional advice from a tax or BAS agent.
About The Author: Artur Osadchiy
Artur is a Certified Practising Accountant with over 30 years’ experience working as a trusted advisor to 600+ clients across Australia. Based in Melbourne, he started Tax Window with his wife Marina in 2009 and leads the firm’s tax and accounting team. In his free time, Artur enjoys watching the AFL (go Kangas!) and spending time with family.
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