Lodging Your First BAS: A Plain English Walkthrough

Your first BAS looks intimidating. It's a form full of codes like G1, 1A, and W1 with zero explanation of what they mean. This walkthrough covers every step from GST registration to hitting submit.

Step 1: Register for GST

You must register for GST if your business turnover is $75,000 or more per year ($150,000 for non-profits). If you're under that threshold, registration is voluntary.

Why register voluntarily? You can claim back the GST on your business purchases. If you spend a lot on tools, materials, or equipment, the refunds can add up. The trade-off: you now have to charge GST on your sales and lodge BAS every quarter (or month).

Register through the Australian Business Register or call the ATO on 13 28 66. You'll need your ABN. Registration takes effect from the date you choose, but you can't backdate it more than four years.

Step 2: Link Your ABN to myGov

Go to my.gov.au and sign in (or create an account). Link the ATO to your myGov account. You'll need to verify your identity, which usually means answering questions from a recent tax return or providing a Notice of Assessment number.

Once linked, you can access ATO Online Services. This is where you'll lodge your BAS.

Step 3: Choose Your Reporting Method

The ATO gives you two options for calculating GST:

Accounts Method (Recommended)

You add up the actual GST from each invoice and receipt. Your accounting software (Xero, MYOB, QuickBooks) does this automatically if your transactions are coded correctly. This method is more accurate and usually results in a lower GST bill.

Calculation Method

You take your total sales, divide by 11 to get GST collected, then do the same for purchases. It's faster if you don't use accounting software, but less precise. You can't use this method if your turnover is over $10 million.

Step 4: Understand What Goes in Each Field

Here are the GST fields you'll fill in on your BAS. Every BAS has these.

G1 - Total Sales

Your total business income for the period, including GST. This covers everything: invoices paid, cash sales, online payments. If you invoiced $11,000 (including $1,000 GST), the full $11,000 goes here.

G2 - Export Sales

Sales to overseas customers. These are GST-free. If you don't export anything, put $0.

G3 - Other GST-Free Sales

Sales that are GST-free by category: fresh food, medical services, education, some financial services. Most tradies and service businesses put $0 here.

1A - GST on Sales (GST Collected)

The total GST you collected from customers during the period. If your total sales were $55,000 (including GST), your 1A figure is $5,000.

1B - GST on Purchases (GST Paid)

The total GST you paid on business purchases. Materials, fuel, tools, software subscriptions, accountant fees. Only include GST from purchases that are genuinely for your business.

Step 5: PAYG Withholding (If You Have Employees)

If you employ staff, your BAS also includes PAYG withholding. This is the tax you've already taken out of your employees' wages.

The key fields:

• W1: Total salary, wages, and other payments you've made to employees
• W2: The total tax withheld from those payments

Your payroll software calculates these automatically. If you're a sole trader with no employees, these fields won't appear on your BAS.

Step 6: PAYG Instalments (Pre-paying Your Own Tax)

The ATO may ask you to pay quarterly instalments toward your own income tax. This is separate from GST and separate from employee withholding.

You'll see either:

• T7 (Instalment amount): The ATO tells you how much to pay. You can vary it if your income has changed significantly.
• T8 (Instalment rate): The ATO gives you a percentage. You multiply it by your income for the quarter.

If this is your very first BAS, you probably won't have PAYG instalments yet. The ATO adds them after your first tax return shows you owe more than $500.

Step 7: Submit Your BAS

Log into ATO Online Services through myGov. Select "Lodge BAS" and choose the correct period. The form will pre-fill some fields. Check them against your records, fill in the rest, and hit submit.

You can also lodge through:

• Accounting software: Xero, MYOB, and QuickBooks can lodge directly with the ATO via Standard Business Reporting (SBR)
• Your BAS agent or tax agent: They lodge on your behalf. Typical cost is $150 to $400 per quarter.
• Phone: Call 13 72 26 for the automated lodgement service (quarterly lodgers only, and only if your BAS has four or fewer fields)

Step 8: Pay What You Owe

If your BAS shows an amount owing, you need to pay by the same due date as lodgement. Check all 2026 deadlines here.

Payment options:

• BPAY: Use the biller code and reference number on your BAS. Allow 1 to 2 business days for processing.
• Direct debit: Set this up through ATO Online Services. The ATO takes the money on the due date.
• Credit/debit card: Pay through the ATO's payment portal. A card surcharge of around 0.4% to 1.5% applies.
• Australia Post: Take your payment slip to any post office. Cash, cheque, or EFTPOS accepted.

If you can't pay the full amount, call the ATO on 13 11 42 before the due date. They can set up a payment plan, and you'll avoid the harshest penalties if you're upfront about it.

Step 9: Keep Your Records

The ATO requires you to keep all business records for 5 years from the date you lodge your BAS (or the date it was due, whichever is later).

That includes:

• Tax invoices for all purchases over $82.50 (including GST)
• Sales invoices and receipts
• Bank statements
• BAS lodgement confirmations
• Payroll records (if applicable)

Digital records are fine. Take photos of paper receipts and store them in a cloud folder organised by quarter. If you ever get audited, "I lost the receipt" is not an answer the ATO accepts.