You’ve done the work, submitted your BAS, and moved on. But what if there’s a mistake hiding in your numbers?
It could be something as simple as flipping two digits, classifying a transaction incorrectly, or even double-counting an expense. These small errors might not seem like a big deal, but over time, they can add up. You could be overpaying taxes, losing out on GST credits, or even putting yourself at risk of an ATO audit.
And then there’s the other side of the equation—sometimes, you didn’t make a mistake at all, but something changed after you lodged your BAS. Maybe a customer returned goods. Maybe you adjusted an invoice amount. In these cases, you’re not fixing an error—you’re making an adjustment.
So, how do you know what’s what? And more importantly, how do you correct a BAS mistake properly? Let’s get into it.
Mistake or Adjustment: What’s the Difference?
First things first—before you correct anything, you need to know whether you’re dealing with a mistake or an adjustment.
A mistake is when you get something wrong at the time of lodgment. Maybe you misclassified a taxable sale as GST-free or made a clerical error in your calculations.
An adjustment happens when your original lodgment was correct, but something changed afterwards—like a customer returning goods, altering the price, or voiding a sale.
Why does this matter? Because the way you fix each one is different.
Common BAS Mistakes (And How to Spot Them)
Ever feel like something’s off with your BAS but can’t quite put your finger on it? Here are some of the most common mistakes:
Transposition errors – Accidentally flipping numbers (e.g., entering $3,210 instead of $3,120).
Misclassifying GST – Treating a GST-free sale as taxable (or vice versa).
Double counting purchases – Entering expenses more than once.
Forgetting to include adjustments from previous periods – Not carrying forward necessary corrections.
How to Correct a BAS Mistake
The good news? Many GST and fuel tax credit mistakes can be corrected in your next BAS. However, the right method depends on whether the mistake is a credit error (where the ATO owes you) or a debit error (where you owe the ATO).
Option 1: Fix It in Your Next BAS
For certain mistakes, you can simply make the correction in your next BAS instead of revising a previous one. This is often the easiest approach and saves you from dealing with unnecessary paperwork.
Option 2: Lodge a Revision
If you can’t fix the mistake in your next BAS—maybe because the amount exceeds ATO correction limits—you’ll need to revise the original BAS. You can do this through:
- Online Services for Business
- Standard Business Reporting (SBR) enabled software
- MyGov (for sole traders linked to the ATO)
- Calling the ATO on 13 28 66 to request a revision form
Not sure which route to take? If in doubt, checking the ATO’s guidelines or seeking professional advice is always a smart move.
When to Make an Adjustment
Unlike a mistake, an adjustment happens when something changes after you lodge your BAS. This could be due to:
- A price change – You issued an invoice, but the final sale price was adjusted.
- A sale being cancelled – A customer returned goods, reducing the taxable amount.
- A purchase refund – You originally claimed GST on an expense but later received a refund.
In these cases, adjustments are usually reported in your next BAS for the current reporting period.
Correcting PAYG Withholding Errors
If you’re an employer, PAYG withholding errors can be tricky. Maybe you over-reported the tax withheld from employee wages, or under-reported and now need to correct it. Here’s how to fix it:
- Revise the earlier BAS to reflect the correct amount.
- Carry forward the correction into the current period’s BAS (subject to ATO limits).
For businesses using Single Touch Payroll (STP), errors should be fixed directly in your payroll reporting system.
The Cost of Ignoring BAS Mistakes
Still thinking of letting that minor error slide? Think again. Failing to correct mistakes could mean:
- Overpaying taxes – Why give the ATO more money than necessary?
- ATO penalties or audits – If errors accumulate, you could find yourself under the tax office’s microscope.
- Cash flow issues – If you’ve over-reported GST, you might be missing out on cash that’s rightfully yours.
Correcting BAS mistakes is more than just a compliance task—it’s about protecting your bottom line.
Need Help? Here’s Where to Go
If fixing BAS mistakes feels overwhelming, you’re not alone. The good news is that you have options:
Use the ATO’s Online Services – Quick and convenient for most corrections.
Call the ATO for guidance – They can clarify correction rules and eligibility.
Talk to Clear Tax Accountants – If your situation is complex, professional help could save you time and money. You can reach out to us and our experienced team will help you find a solution after analysing your situation.
Mistakes happen, but leaving them uncorrected is a choice. The next time you spot an error in your BAS, take action—you’ll thank yourself later.
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