Straight answers on lodgement dates, GST, penalties and sole trader obligations for Australian small businesses.
The ATO sets quarterly BAS deadlines on the 28th of the month after each quarter ends. For 2026, the quarterly dates are:
Monthly lodgers must lodge by the 21st of the following month. If you lodge through a registered tax agent, you may get extra time on some quarters.
Read more about how BAS deadlines work and what to prepare.
Log into myGov and go to the ATO linked service. Select Lodge, then Activity Statements from the menu. Pick the period you need to lodge.
Fill in your GST amounts at labels G1, 1A, and 1B. If you report PAYG instalments or PAYG withholding, fill those sections too. Review the totals, then submit.
You will get a receipt number as confirmation. Keep that receipt with your records. If you run into trouble, a registered BAS agent can lodge on your behalf.
You must lodge a BAS if you are registered for GST. GST registration is required once your annual turnover hits $75,000 or more. Below that threshold, registration is optional.
If you have voluntarily registered for GST, you still need to lodge every period - even if your turnover drops below the threshold. Skipping a period triggers ATO follow-up.
If you are not registered for GST but have PAYG withholding obligations (such as paying employees), you will also receive a BAS. Check our sole trader BAS guide for more detail.
The ATO charges a Failure to Lodge (FTL) penalty. The penalty starts at one penalty unit ($330 as of 2025-26) for each 28-day period the BAS is overdue, up to a maximum of five penalty units ($1,650).
You will also owe General Interest Charge (GIC) on any unpaid tax from the original due date. The GIC rate changes each quarter and sits well above normal interest rates.
The ATO may remit the penalty if you have a good compliance history and lodge quickly. Contact them before the deadline if you know you will be late.
Most small businesses use the cash or accrual method for GST reporting. Here is the core calculation:
If 1A is larger than 1B, you owe the ATO. If 1B is larger, you get a refund. Keep all tax invoices for purchases over $82.50 (GST inclusive) as proof of your claims.
Read our GST reporting breakdown for worked examples.
You can apply for a deferral by contacting the ATO before the due date. Call the ATO business line on 13 28 66 and explain your circumstances.
The ATO may grant extra time if you have been affected by a natural disaster, serious illness, or other exceptional events. They are more likely to help if you have a clean lodgement history.
Using a registered tax or BAS agent is another option. Agents often have later lodgement deadlines built into their schedules, which gives you extra weeks without needing to apply for anything.