How to Do a BAS Statement (Step-by-Step)

A Business Activity Statement (BAS) is the form Australian businesses use to report and pay several tax obligations to the Australian Taxation Office (ATO) — most commonly goods and services tax (GST) and pay as you go (PAYG) withholding or instalments. If you are registered for GST, you need to lodge a BAS at the frequency the ATO has set for your business (monthly, quarterly, or annually). This guide walks through the process from gathering your records to lodging the finished statement. For the authoritative rules, always refer to the ATO.

Step 1: Know your reporting period and obligations

Before you start, confirm two things: the period the BAS covers and which obligations apply to you. The ATO tells you your reporting cycle when you register, and the relevant fields are pre-printed on your statement. Most small businesses report quarterly. Depending on your registration, your BAS may include:

• GST — what you collected on sales and what you paid on purchases.
• PAYG withholding — amounts you held back from employees' wages.
• PAYG instalments — prepayments toward your own income tax.
• Other items such as fuel tax credits, where they apply to you.

Only complete the sections that apply. The ATO publishes detailed BAS instructions for each field, and you should read those alongside this guide.

Step 2: Gather your records

A BAS is only as accurate as the records behind it. For the reporting period, pull together:

• Sales invoices and receipts showing GST collected.
• Purchase invoices and expense receipts showing GST paid.
• Payroll records for any PAYG withholding.
• Bank statements covering the whole period, so nothing is missed.

Bank statements are useful as a cross-check: they confirm money actually moved and help you catch transactions you forgot to record. If your statements are locked in PDFs, you can turn them into tidy spreadsheet rows first — see how to prepare a BAS from bank statements, or run the files through the free bank statement converter so every line is sortable.

Step 3: Calculate GST collected and GST paid

This is the core of most BAS lodgements.

1. Total your GST-inclusive sales for the period. From these, work out the GST you collected. The GST portion of a sale is generally one-eleventh of the GST-inclusive price, but check the ATO guidance for GST-free and input-taxed sales, which are treated differently.
2. Total your GST-inclusive purchases where you are entitled to a credit, and work out the GST you paid (GST credits, also called input tax credits).
3. The difference between GST collected and GST credits is broadly what you owe — or, if your GST credits exceed the GST you collected, the net amount may be refundable. A refundable amount is not always paid out as cash, though: the ATO can offset it against other tax debts you owe before refunding any remainder. Check the current ATO rules for how refunds and offsets apply.

Keep your sales and purchase totals separate and well documented. If you make a mistake, having clean source figures makes corrections easier.

Step 4: Work out PAYG amounts

If you employ staff, add up the PAYG withholding — the tax you withheld from wages during the period. This figure comes from your payroll records.

If the ATO has registered you for PAYG instalments, your statement will show either an instalment amount the ATO has calculated for you or a rate to apply to your income. Follow the method indicated on your statement and in the ATO instructions. These instalments go toward your end-of-year income tax, so they are separate from GST.

Step 5: Complete the form fields

With your figures ready, fill in the statement. Work through it section by section rather than jumping around:

• Enter your total sales and the GST on sales in the GST section.
• Enter your purchases and the GST on purchases (your GST credits).
• Enter your PAYG withholding and PAYG instalment amounts in their sections.
• Let the form total everything into the net amount you owe or are owed.

The exact field labels and codes are set out on the ATO statement itself and in the accompanying BAS instructions — use those as your reference rather than memorising label numbers, because they are laid out clearly on the form. Enter whole-dollar amounts as the instructions direct, and leave non-applicable fields blank rather than entering a zero unless told otherwise.

Step 6: Review before you lodge

Mistakes on a BAS can mean paying too much, too little, or having to revise later. Before lodging, run a quick review:

• Do your GST figures reconcile with your sales and purchase totals?
• Have you included the full period and excluded transactions from other periods?
• Do the PAYG figures match your payroll and ATO-issued instalment details?
• Does the net amount look reasonable compared with previous statements?

Cross-checking against your bank statements is a good final sanity check that the cash movements line up with what you have reported.

Step 7: Lodge and pay by the due date

Lodge your completed BAS by the due date shown on the statement. The ATO offers several lodgement channels, including online services for business, the option to lodge through a registered BAS or tax agent, and other methods set out in their guidance. Whichever channel you use, keep a copy of the lodged statement and the supporting records.

Pay any amount owing by the due date to avoid interest or penalties. If your BAS results in a refundable amount, the ATO may first offset it against any other tax debts you owe; any remaining refund is generally paid to your nominated bank account. If you find an error after lodging, the ATO explains how to correct or revise a BAS — check the current rules on the ATO website.

Keeping it manageable next time

The BAS gets easier when your records are clean and your bank transactions are already in a spreadsheet you can filter and total. Establishing that habit each period — rather than scrambling at the deadline — turns BAS time into a short review instead of a reconstruction. When you are ready to start the next one, you can prepare your BAS from bank statements or convert your files with the bank statement converter and work from clean rows.

This guide is general information, not tax advice. For rules specific to your business, refer to the ATO or speak with a registered BAS or tax agent.