How do I lodge my BAS online?

Sole traders lodge through myGov, linked to the ATO. Companies, partnerships and trusts use Online services for business, signing in with a Digital ID (myID) linked to the business in Relationship Authorisation Manager. You can also lodge straight from accounting software such as Xero, MYOB or QuickBooks, or through a registered tax or BAS agent.

What goes in G1, 1A and 1B on a BAS?

G1 is your total sales for the period, including GST-free sales and exports, and including GST if your records do (tick the box saying so). 1A is the GST you charged on your sales. 1B is the GST you paid on your business purchases. If 1A is more than 1B you pay the difference; if 1B is more, the ATO refunds you.

Do I need to lodge a BAS if I had no sales?

Yes. If you're registered for GST you must lodge a BAS for every period, even with nothing to report. A nil BAS can be lodged online in a few clicks, or by phone on the ATO's automated line, 13 72 26.

By BPAY (biller code 75556) or bank transfer using the payment reference number (PRN) on your BAS, by card (a fee applies), or in person at Australia Post. Payment is due on the same day as the lodgment. If you can't pay in full, lodge on time anyway and set up a payment plan in ATO online services.

The default GST reporting for businesses with GST turnover under A$10 million. You only report three GST labels: G1 total sales, 1A GST on sales and 1B GST on purchases. Larger businesses also report exports (G2), other GST-free sales (G3), capital purchases (G10) and non-capital purchases (G11).

How do I fix a mistake on a BAS I've already lodged?

Many GST errors can be corrected on a later BAS, if they're within the ATO's time and value limits, by adjusting the figures on the next activity statement you lodge. Larger or older mistakes, or ones that mean you underpaid, may need the original BAS revised through online services or your agent.

How to Lodge a BAS: G1, 1A and 1B Explained

Short answer: for GST, most small businesses fill in just three boxes on their business activity statement (BAS): G1 total sales, 1A GST on sales and 1B GST on purchases. You pay 1A minus 1B, or get a refund if it’s negative. Lodge through myGov (sole traders), Online services for business (companies), your accounting software or a tax or BAS agent, and pay by BPAY with your payment reference number. Lodge every period, even with nothing to report.

This guide covers the GST part of the BAS for registered businesses, as of 12 November 2026. For when each BAS is due, see BAS due dates.

What’s on your BAS

A BAS is personalised: it only shows the sections that apply to you.

Section	What it covers	Who sees it
GST	G1, 1A and 1B (plus G2, G3, G10, G11 on full reporting)	Everyone registered for GST
PAYG withholding	Tax withheld from employees’ wages (W1, W2)	Employers
PAYG instalments	Prepaid income tax the ATO asks you to pay	Businesses and sole traders in the instalment system
Fuel tax credits, wine tax, luxury car tax, FBT instalments	Specific industries	Only if you’re registered for them

This guide covers the GST section. Your accountant or software handles the rest the same way.

The GST labels

Businesses with GST turnover under A$10 million use simpler BAS, which needs only three GST labels:

Label	What goes in	Common mistakes
G1 Total sales	All sales for the period: taxable, GST-free and exports. Tick Yes if the figure includes GST	Leaving out exports or GST-free sales. Including sales made by marketplaces on your behalf
1A GST on sales	The GST you charged on taxable sales: one-eleventh of GST-inclusive taxable sales	Working out GST on all of G1 instead of only the taxable sales
1B GST on purchases	The GST you paid on business purchases, backed by tax invoices for anything over A$82.50	Claiming GST on purchases without GST (overseas software, bank fees, wages, insurance stamp duty)

Businesses over A$10 million (or that choose full reporting) also report G2 export sales, G3 other GST-free sales, G10 capital purchases and G11 non-capital purchases.

Report whole dollars: drop the cents, don’t round up.

Where the numbers come from for online sellers

Shopify, WooCommerce, BigCommerce: export the period’s orders with tax by country. Australian orders give you GST charged (1A). Orders shipped overseas are GST-free exports: in G1, not in 1A.
Marketplaces: for an Australian seller, Amazon, eBay and Etsy don’t charge GST on your domestic sales, so those sales and their GST are yours to report. Their seller fees usually include GST, which you can claim in 1B with their tax invoice.
Payment processors: some charge GST on their fees and some don’t, because payment processing can be an input-taxed financial supply. Claim only the GST shown on the processor’s tax invoice.
Imports: GST you paid at the border on stock you imported goes in 1B, using the import declaration as your evidence.
Overseas software: subscriptions from overseas suppliers that didn’t charge GST (because you gave them your ABN) have no GST to claim.

How to lodge, step by step

Reconcile the period. Make sure every sale and purchase is in your books, and match bank deposits to orders.
Run your BAS report in Xero, MYOB or QuickBooks, or work out G1, 1A and 1B from your exports.
Sign in to lodge. Sole traders: myGov, linked to the ATO. Companies and partnerships: Online services for business with your myID, authorised for the business in RAM. Or lodge directly from your accounting software.
Open the activity statement for the period.
Enter G1, 1A and 1B (and any other sections), check the summary, and lodge.
Note your payment reference number (PRN) and pay by the due date.

Prefer someone else to do it? A registered tax or BAS agent lodges on your behalf and usually gets later due dates.

Worked example: a quarterly simpler BAS

Fitzroy Wick Co. sells candles on Shopify from Melbourne and is registered for GST. For January–March 2027 its Shopify export and receipts show:

	Amount (including GST)	GST
Australian orders	A$25,000	A$2,272.73 (A$25,000 ÷ 11)
Orders to New Zealand, the UK and the US (GST-free exports)	A$2,500	A$0
Wax, wicks and jars from Australian suppliers	A$6,600	A$600.00
Packaging	A$1,320	A$120.00
Bookkeeper	A$550	A$50.00
Shopify plan billed by Shopify’s overseas entity, no GST (ABN supplied)	A$480	A$0

Its BAS:

Label	Amount
G1 Total sales (includes GST: Yes)	A$27,500
1A GST on sales	A$2,272
1B GST on purchases	A$770
Payable	A$1,502

It lodges online itself, so with the two-week concession it lodges and pays by 12 May 2027 instead of 28 April.

Paying your BAS

Method	Details
BPAY	Biller code 75556, with your PRN as the reference
Bank transfer	To the ATO’s account, quoting your PRN
Card	Online, with a card fee
Australia Post	In person, with your BAS payment slip

The payment is due on the same day as the lodgment. If 1B is more than 1A, the ATO refunds the difference to your nominated bank account, usually within a couple of weeks, after setting off any other debts you owe it.

Can’t pay? Lodge on time anyway: the failure-to-lodge penalty is separate from interest on the debt. Then set up a payment plan in ATO online services.

Nil BAS

If you’re registered and had no sales or purchases in the period, you still lodge, with zero at every label:

Online: in myGov, Online services for business or your software, choose the nil option.
By phone: the ATO’s automated line, 13 72 26, with your BAS details to hand.

Several nil quarters in a row? If you’ve stopped trading, consider cancelling your GST registration.

Fixing mistakes

Correct it on a later BAS if the error is within the ATO’s time and value limits: adjust your next G1, 1A or 1B and keep a note of why.
Revise the original BAS for larger or older errors, through online services or your agent.
Tell the ATO early. A voluntary disclosure before an audit usually means lower penalties.

Official sources

How to lodge your BAS, Australian Taxation Office
Completing your BAS for GST, Australian Taxation Office
Lodging your BAS or annual GST return, Australian Taxation Office
Due dates for lodging and paying your BAS, Australian Taxation Office