Treating GST as what it actually is: money held on the ATO's behalf
A customer pays your invoice. The full amount lands in your bank account, GST included.
It's tempting to see all of it as revenue. Only part of it actually is.
Of everything a GST-registered business collects, a slice was never really the business's income at all — it was collected on the ATO's behalf, and it's due back to them, regardless of how the rest of the month goes.
The short answer
When you charge GST, you're acting as a collection agent for the ATO. The GST component of every sale isn't business revenue — it's money you're holding temporarily until your next BAS, at which point (netted against any GST credits on your own purchases) it's paid across. Treating it as available cash is one of the most common ways GST-registered businesses end up short at BAS time.
Why it's so easy to get this wrong
The money looks identical sitting in your bank account — there's no separate “GST” pile visually distinguishing it from genuine income. It moves and spends exactly the same way, right up until the BAS is due and a chunk of what felt like available cash turns out to already have another job.
A simple example
A business invoices $22,000 including GST for the month — $2,000 of that is GST collected on behalf of the ATO, leaving $20,000 in genuine revenue. If the business also paid $6,600 (including $600 GST) on business purchases during the same period, it can claim that $600 back as a GST credit.
Net GST owing for the BAS: $2,000 collected minus $600 credit — $1,400 payable. That $1,400 was never really available to spend, no matter how the bank balance looked along the way.
How to actually manage it
Separate it the moment it arrives. Move the GST component of each payment into a dedicated account as soon as it's received, not at BAS time.
Let accounting software track it automatically. Modern software tracks GST on every transaction as it happens, so the true position is always visible rather than reconstructed later.
Net it against credits, but don't assume the credit before it's confirmed. You're entitled to claim back GST on business purchases, but that offset is calculated at BAS time — don't spend the anticipated credit before it's actually netted off.
Review your GST position regularly, not just quarterly. A monthly glance at what's accumulating avoids a large, unexpected number appearing only when the BAS is due.
Why this discipline matters beyond just avoiding a shortfall
A business that consistently treats GST as its own money tends to run structurally short at every BAS cycle — not because the business isn't doing well, but because a portion of its apparent cash was always spoken for. Separating it properly doesn't just prevent a nasty surprise; it gives a much more honest, accurate read on how the business is actually performing.
A quick self-check
Do I know, right now, roughly how much GST I'm currently holding for the ATO?
Is that amount sitting in a separate account, or mixed into general operating cash?
Am I confident my next BAS won't be a surprise?
Is my accounting software tracking GST automatically, or am I reconstructing it manually?
When should you get professional help?
you're not confident your GST position is being tracked accurately throughout the quarter;
you've been caught short at BAS time and want a system that prevents it recurring;
you're not sure how GST credits on your own purchases actually reduce what you owe; or
you want your accounting software set up to separate GST automatically as transactions occur.
Continue learning
→ Understanding BAS — What Am I Actually Reporting and Paying?
→ How Much Should I Put Aside for BAS and Tax?
→ Should I Open a Separate Business Bank Account?
SKC Accounting | Knowledge Centre | Knowledge Guide 025
Last reviewed: August 2026
General information only. This guide does not take into account your individual circumstances and is not a substitute for professional accounting, taxation, legal or financial advice.