Understanding BAS — What Am I Actually Reporting and Paying?

A Business Activity Statement (BAS) is how GST-registered businesses report and pay several tax obligations to the ATO in one combined statement — most commonly GST, PAYG withholding (if you have employees) and PAYG instalments (prepayments toward your own income tax). The ATO sends it roughly two weeks before your reporting period ends, and it's due back, with any payment, by the date shown on it.

• GST on sales and purchases. The GST you've collected from customers, minus the GST credits you're entitled to on business purchases — the difference is what you pay, or in some cases, get refunded.

• PAYG withholding. If you have employees, the tax withheld from their wages on your behalf and remitted to the ATO.

• PAYG instalments. Prepayments toward your own income tax for the year, based on an instalment rate the ATO calculates from your previous year's income — so tax time isn't one large, unexpected bill.

• Other taxes, where relevant. Fringe Benefits Tax instalments, Luxury Car Tax, Wine Equalisation Tax or Fuel Tax Credits, depending on your business.

Most small businesses only deal with GST and, if they employ anyone, PAYG withholding — the ATO's “Simpler BAS” approach means most small businesses only need to complete a small number of GST fields.

Quarterly due dates fall on the 28th of the month following the quarter's end, with the December quarter extended to 28 February. If a registered BAS agent lodges on your behalf, extended deadlines generally apply — for both quarterly and annual reporting.

A business collects $8,000 in GST from sales during the quarter, and has paid $3,000 in GST as part of its own business purchases. Its BAS reports both figures, and it pays the ATO the $5,000 difference — the net GST owing for the period.

• Reconcile your accounts before you prepare the BAS, not after — errors caught before lodgement are far easier to fix than after.

• Keep GST tracked separately throughout the quarter, not reconstructed at the deadline.

• Confirm STP payroll figures match your PAYG withholding totals if you have employees.

• If you make a mistake, it can generally be corrected in your next BAS or by revising the original — it isn't the end of the world, but it's worth fixing promptly.

• Do I know my BAS due date for this period, and is it in my calendar?

• Have I reconciled my accounts before starting to prepare it?

• Am I clear on which taxes actually apply to my BAS — GST only, or GST plus PAYG?

• If I use a bookkeeper or agent, have I sent them everything they need with enough lead time?

The ATO provides full guidance on completing and lodging your BAS.

ato.gov.au — Business activity statements (BAS) https://www.ato.gov.au/businesses-and-organisations/preparing-lodging-and-paying/business-activity-statements-bas

• you're preparing your first BAS and want to make sure your GST tracking is set up correctly;

• your BAS includes obligations beyond GST — PAYG, FBT, WET or LCT — and you want them handled properly;

• you've made an error on a previously lodged BAS; or

• you'd prefer a registered BAS agent to lodge on your behalf, with the compliance protection that comes with it.

→ How Much Should I Put Aside for BAS and Tax?

→ GST Collected Isn't Really My Money — So How Should I Manage It?

→ What Happens If I Can't Pay My BAS or Tax on Time?

SKC Accounting | Knowledge Centre | Knowledge Guide 023

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.