BAS Reporting
How the Business Activity Statement works for GST, PAYG instalments, and PAYG withholding: reporting frequencies, Simpler BAS vs full BAS, lodgement methods, corrections, record-keeping requirements, and worked examples showing exactly how the labels flow.
A BAS is the form the ATO issues for businesses to report and pay GST, PAYG instalments, PAYG withholding, and other activity-based taxes. Most sole traders report GST and PAYG instalments on a quarterly BAS using Simpler BAS (three GST labels: G1, 1A, 1B), with PAYG instalment labels alongside. You must lodge a BAS for each reporting period even if there is no activity (a nil BAS). A single payment covers both GST and PAYG instalment obligations for the quarter.
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Guidance, not advice. We explain the rules, we don't assess your situation. Always seek financial or tax advice from your accountant, or contact ATO. Read our editorial scope →
What a BAS covers
A BAS is the ATO's multi-purpose activity statement for businesses with an ABN. It can include GST, PAYG instalments (income tax prepayments on untaxed business and investment income), PAYG withholding (tax withheld from employee wages and certain contractor payments), fringe benefits tax instalments, luxury car tax, and wine equalisation tax. Most sole traders without employees only see GST and PAYG instalment labels. Once you employ staff or engage contractors without ABNs, PAYG withholding labels (W1, W2, W3 to W5) appear.
Reporting frequency: quarterly, monthly, and annual
The default reporting cycle depends on your GST turnover and registration status.
Quarterly due dates 2025-26
Q1 (July to September): 28 October 2025. Q2 (October to December): 28 February 2026. Q3 (January to March): 28 April 2026. Q4 (April to June): 28 July 2026. Tax agent clients may have lodgement concessions on some quarters (typically Q1 extends to 25 November, Q3 to 26 May, Q4 to 25 August). There is no agent concession for the Q2 February deadline.
Simpler BAS vs full BAS
Simpler BAS has been the default for businesses with GST turnover under $10 million since 1 July 2017. It reduces the GST portion of the form to three labels.
When full BAS might be needed
Businesses with GST turnover of $10 million or more, or those with significant exports, substantial input-taxed supplies (financial services, residential rents), or complex adjustments. A small business can request full reporting, but this only makes sense where the extra detail materially affects analysis or ATO risk profile. Most sole traders should stay on Simpler BAS.
PAYG instalments on the BAS
PAYG instalments are income tax prepayments built into the BAS for most self-employed taxpayers. The ATO calculates the instalment using either a fixed dollar amount (labels T7/T8 feeding to 5A) or an instalment rate applied to reported income (labels T1, T2/T3, T11, feeding to 5A). A single payment to the ATO covers both the net GST position and the PAYG instalment for the quarter.
Varying your instalment on the BAS
If your expected income drops or rises, you can vary the PAYG instalment on the BAS by entering a different amount at T7/T8 or a different rate at T3. The ATO's safe harbour protects you from penalties provided your total varied instalments for the year come to at least 85% of your final tax on instalment income. Keep records of the basis for any variation.
PAYG withholding for employers
If you employ staff or pay certain contractors (including those who do not quote an ABN), you must withhold tax and report it on the BAS.
Single Touch Payroll (STP) interaction
Most employers now report individual wage and withholding data through STP each pay cycle. The BAS still requires you to summarise total withholding for the period and pay the withheld amounts by the due date. STP does not replace the BAS payment obligation; it replaces end-of-year payment summaries and provides the ATO with real-time data.
Lodgement methods
The ATO strongly prefers electronic lodgement. Most BAS are lodged through one of five channels.
Corrections and amendments
Errors on a prior BAS can generally be corrected on a later BAS by making a credit or debit adjustment. The legislation allows a four-year amendment period for activity statements. Where the correction increases the tax payable for an earlier period, the ATO may apply General Interest Charge from the original due date until payment. Large or complex corrections may require a formal revision request rather than a self-correction on the next BAS.
Worked examples
Two scenarios showing how the BAS labels connect for a typical sole trader quarter.
Example 1: quarterly BAS with GST and PAYG instalment
Deepika, a sole trader marketing consultant in Melbourne, is GST-registered and on Simpler BAS with a quarterly PAYG instalment of $2,000. Her Q1 figures: total sales $33,000 (GST-inclusive), total business purchases $11,000 (GST-inclusive). G1: $33,000. 1A (GST on sales): $33,000 divided by 11 = $3,000. 1B (GST on purchases): $11,000 divided by 11 = $1,000. Net GST payable: $2,000. PAYG instalment at T7: $2,000. Total BAS payment: $4,000, due 28 October.
Example 2: BAS with GST refund (start-up phase)
Jackson, a new sole trader web developer in Newcastle, is GST-registered from day one with heavy set-up costs. Q1 figures: sales $5,500 (GST-inclusive), purchases $22,000 (GST-inclusive, equipment and website hosting). 1A: $500. 1B: $2,000. Net GST: ATO owes Jackson $1,500 (refund position). No PAYG instalment labels (first year, ATO has not yet started instalments). The BAS shows a net refund of $1,500, paid into his nominated bank account. This is typical of start-ups: large early capital costs generate GST refunds before net GST becomes payable as revenue grows.
Statute references
- Taxation Administration Act 1953, Schedule 1 (BAS administration, PAYG systems, penalties, GIC, record-keeping)
- A New Tax System (Goods and Services Tax) Act 1999 (GST obligations reported through BAS)
- ATO Simpler BAS guidance (labels, qualification, transaction classification)
Frequently asked questions
Do I need to lodge a BAS if I had no sales or purchases in a quarter?+
What is the difference between Simpler BAS and full BAS?+
Can I correct a mistake on a previous BAS?+
How does PAYG instalment integrate with GST on the BAS?+
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