How to Complete and Lodge a Business Activity Statement

To lodge a Business Activity Statement, log in to Online services for business (or myGov if you are a sole trader), fill in the GST, PAYG, and any other labels that apply to your registrations, then submit by your due date and pay any amount owing. The form uses a labelling system, but the core calculation is simple: GST you collected on sales, minus GST you paid on business purchases, equals what you owe or what the ATO owes you.

Before You Start: Records and Accounting Method

Completing a BAS accurately depends on having organised records for the whole reporting period. Gather your tax invoices for every sale and every business purchase, plus payroll records showing wages paid and amounts withheld. These are the evidence behind every figure on the form. Most business records must be kept for five years from the date you lodge,¹ and some company and employee records for seven years.²

You also need to know which accounting method you use for GST, because it determines when a transaction is reported. Under the cash method, you report GST when you actually receive payment for a sale or pay for a purchase. Under accrual (non-cash) accounting, you report GST when you issue or receive an invoice, regardless of whether money has changed hands. Most small businesses use cash accounting because it matches the way they think about money. If you want to switch methods, the change can only take effect on the first day of a tax period.³

Filling In the GST Labels

You access your BAS through Online services for business, or myGov if you are a sole trader. SBR-enabled software can also lodge directly from your accounting package.⁴ The system displays the statement assigned to your business based on your registrations. Every business completes three core GST labels:

G1 — Total sales. Enter the total price of all goods and services you sold during the period, including the GST component. This figure includes taxable sales, GST-free sales, and input taxed sales.⁵
1A — GST on sales. The total GST you collected on taxable sales during the period.
1B — GST on purchases. The total GST you paid on business-related purchases you can claim a credit for.

Subtract 1B from 1A. If 1A is larger, you owe the difference. If 1B is larger, the ATO owes you a refund. This is where businesses with heavy capital expenditure in a quarter often find they are owed money back. All amounts must be rounded down to whole dollars, with no cents shown.⁶

GST-Free and Input Taxed Sales

Not everything you sell carries GST, but all sales still go into G1. The distinction matters for your credits at 1B. GST-free sales carry no GST to the customer, but you can still claim GST credits on the purchases you made to generate them. Common examples are most basic food, medical services, education courses, childcare, and exports.⁵

Input taxed sales also carry no GST, but you generally cannot claim GST credits on related purchases. The most common are residential rent, sales of existing residential property, and financial transactions like lending money or selling shares.⁵ If you make a mix of taxable and input taxed sales, you can only claim a partial GST credit on shared expenses. Getting this classification wrong is one of the most common BAS mistakes and the one most likely to trigger an ATO adjustment.

PAYG Labels If They Apply to You

A BAS also covers PAYG withholding (tax taken from employee wages) and PAYG instalments (prepayments toward your own income tax). Whether these labels appear depends on the roles the ATO has on file for your business.⁷

PAYG Withholding

If you have employees, you report at W1 the total salary, wages and other payments made during the period, and at W2 the amount you withheld.⁷ If you report payroll through Single Touch Payroll, the ATO pre-fills W1 and W2 in your electronic BAS from your STP reports.⁸ Check the pre-filled figures against your own payroll records before you lodge. Pre-fill does not cover W3 or W4 (amounts withheld where no ABN was quoted), so those still need manual entry if they apply.

PAYG Instalments

PAYG instalments are separate from withholding. They are prepayments toward your own income tax bill, calculated from your business and investment income. If the ATO has notified you that you need to pay instalments, the relevant labels appear on your BAS. You usually get two options:⁹

Option 1 (fixed amount). The ATO calculates an instalment (shown at T7) based on your prior year. You can vary it at T9 if your income has changed, entering your estimated tax for the year at T8.
Option 2 (income times rate). Enter your actual instalment income at T1, multiply by the ATO’s rate at T2, and enter the result at T11. You can vary the rate at T3 if your circumstances have changed.

Either way, the final instalment amount flows into label 5A. If you varied downward and overpaid in an earlier quarter, you can claim a credit at 5B.

Fuel Tax Credits

If your business uses fuel for activities like running heavy vehicles, machinery, or equipment, you may be eligible to claim fuel tax credits at label 7D. Timing follows your accounting method: under cash, you claim in the period you pay for the fuel; under accrual, in the period you receive the invoice. If fuel was later used for a purpose attracting a lower credit rate, report the adjustment at label 7C to reduce your entitlement.¹⁰

Lodging the Statement

Most businesses lodge electronically through one of three channels:⁴

Online services for business — the ATO’s secure portal for companies, partnerships, and trusts.
myGov — sole traders link to the ATO through their individual myGov account.
SBR-enabled software — accounting packages such as Xero, MYOB, or QuickBooks can lodge directly.

You can also have a registered tax agent or BAS agent lodge on your behalf. Agents often receive extended deadlines, and using a registered agent gives you legal protections you do not get from unregistered preparers.¹¹ Paper lodgment is still possible by mail, but it does not qualify for the two-week online extension.

When you submit electronically, the system generates a receipt number. Keep it. That receipt is your proof of lodgment if there is ever a dispute about timing.

Deadlines and Paying What You Owe

For quarterly lodgers, the due dates are:¹²

Quarter 1 (July–September): 28 October
Quarter 2 (October–December): 28 February
Quarter 3 (January–March): 28 April
Quarter 4 (April–June): 28 July

Lodging online adds two extra weeks for quarters 1, 3, and 4. Quarter 2 does not get that extension because 28 February already includes a built-in one-month extension from the usual 28-day-after-quarter-end pattern.¹² When a due date falls on a weekend or public holiday, you have until the next business day. Monthly lodgers must submit by the 21st of the following month. Annual lodgers submit with their income tax return.

If your BAS shows an amount owing, pay by the same deadline. The ATO accepts BPAY, direct debit, and credit or debit card payments.¹³ Payments can take up to four business days to appear on your ATO account, so do not leave payment until the final day if your method has processing time.¹⁴ If your BAS shows a refund, the ATO pays it into the bank account linked to your registration, and refunds usually process faster when you lodge electronically.

If You Cannot Pay or You Made a Mistake

If you cannot pay in full by the due date, contact the ATO before the deadline rather than ignoring it. You may be able to set up a payment plan that breaks the debt into weekly, fortnightly, or monthly instalments through the ATO’s online services, which include an estimator for your upfront payment, minimum repayment, and expected interest. A payment plan does not freeze the general interest charge; interest keeps accruing on the outstanding balance. The ATO does offer interest-free plans for certain overdue activity statement amounts, so it is worth asking. If you have debts on both your income tax account and your activity statement account, each requires a separate plan. Setting up a plan also means you must keep paying future BAS debts in full and on time, or the plan can be cancelled.¹⁵

Errors happen. Many GST and fuel tax credit mistakes can be fixed on your next BAS instead of revising the original.¹⁶ The ATO distinguishes credit errors (you overclaimed or underreported, so the ATO is owed money) from debit errors (you underclaimed or overpaid). Credit errors can be corrected on a later BAS provided you do so within the four-year period of review.¹⁷ If a mistake cannot be corrected on a later BAS, typically because it falls outside the allowed conditions or involves PAYG amounts that cannot be carried forward, you will need to lodge a formal revision of the original statement through the same online portal. For PAYG withholding errors, employers reporting through STP can sometimes carry forward corrections to the current tax period’s withholding; check the ATO’s STP correction guidance if your error sits on the payroll side.

Penalties for Missing the Deadline

Miss the deadline and the ATO can impose a failure-to-lodge penalty. It accrues at one penalty unit for every 28 days (or part) that the BAS is overdue, up to a maximum of five penalty units. As of November 2024, one penalty unit is $330, so the maximum base penalty is $1,650.¹⁸

That base amount applies to small entities. Medium entities (assessable income or GST turnover between $1 million and $20 million) pay double. Large entities ($20 million or more) pay five times the base.¹⁹ For a large entity five periods overdue, the penalty reaches $8,250. On top of lodgment penalties, any unpaid tax debt accrues a general interest charge. For the January–March 2026 quarter, the GIC rate is 10.65% per annum,²⁰ and it compounds daily, so even a short delay adds up quickly on a large balance.

1
Australian Taxation Office. Records You Need to Keep
2
business.gov.au. Record Keeping
3
Australian Taxation Office. Choosing an Accounting Method for GST
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Australian Taxation Office. How to Lodge Your BAS
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Australian Taxation Office. Simpler BAS GST Bookkeeping Guide
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Victorian Small Business Commissioner. ATO Business Activity Statement Example
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Australian Taxation Office. Pay As You Go (PAYG) Withholding
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Australian Taxation Office. ATO PAYG Withholding Pre-Fill for Activity Statements
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Australian Taxation Office. PAYG Instalments – How to Complete Your Activity Statement
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Australian Taxation Office. How to Complete Your Activity Statement Labels
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business.gov.au. Business Activity Statement
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Australian Taxation Office. Due Dates for Lodging and Paying Your BAS
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Australian Taxation Office. How to Pay
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Australian Taxation Office. Other Payment Options
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Australian Taxation Office. Payment Plans
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Australian Taxation Office. Fixing BAS Mistakes or Making Adjustments
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Australian Taxation Office. Types of GST Errors
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Australian Taxation Office. Penalty Units
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Australian Taxation Office. Failure to Lodge on Time Penalty
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Australian Taxation Office. General Interest Charge (GIC) Rates