Q4 due date for BAS 2025–26: Lock in your 25 August extension before ATO penalties hit

If your business is registered for GST in Australia, all standard self-lodgement deadlines for your Q4 Business Activity Statement, both paper (28 July) and online (11 August), have officially passed. If you have not submitted your return, your entity is now exposed to potential ATO Failure to Lodge (FTL) penalties and general interest charges.

The good news? You have not run out of options. Appointing a registered BAS agent instantly shifts your due date for BAS 2025–26 to 25 August, giving you nearly two extra weeks to reconcile your books, fix accounting errors, and lodge with total peace of mind. Here is how to secure your agent extension today and stop ATO penalties in their track.

What is quarter 4 BAS?

Quarter 4 BAS is the Business Activity Statement for the final quarter of the Australian financial year, covering 1 April to 30 June. Businesses registered for GST may use their BAS to report GST collected and paid, PAYG withholding, PAYG instalments and other applicable tax obligations.

For the 2025–26 financial year, the exact Q4 BAS lodgement and payment deadline depends on whether you lodge yourself or through a registered tax or BAS agent.

When is the Q4 due date for BAS 2025–26?

The Q4 Business Activity Statement covers the final quarter of the 2025–26 financial year (1 April to 30 June 2026). Your exact lodgement and payment deadline depends on how you lodge:

• Self-lodgers (Paper): The standard ATO deadline for paper-based self-lodgements was 28 July 2026.
• Self-lodgers (Online): If you manage and lodge online through ATO Online services or myGov, the ATO offers an additional 2 weeks to lodge and pay your activity statement, pushing your deadline to 11 August 2026.
• Registered agent lodgement: Appointing a registered tax or BAS agent like CleanSlate instantly extends your deadline to 25 August 2026.

These concessions provide valuable time for small business owners to reconcile bank statements, verify GST calculations using our GST calculator, and review PAYG figures accurately before submitting.

What do you need to prepare for your Q4 BAS?

Before lodging your statement accurately, you or your bookkeeping team must have the following financial data prepared:

• GST figures: Total GST collected on sales and GST paid on business purchases throughout the quarter.
• PAYG withholding: Total tax withheld from employee salaries and wages, if you have staff on payroll.
• PAYG instalments: Pre-calculated income tax instalment amounts, where applicable to your business structure.
• Reconciled bank accounts: All business bank and credit card feeds are fully reconciled against your cloud accounting software.
• Complete records: All outstanding sales invoices, supplier bills, and receipts properly entered into your system.

In our experience, the main source of BAS stress is not the actual submission. It is discovered that bank accounts are not reconciled until days before the deadline, leaving little time to fix data entry errors or find missing receipts.

This is where our professional online bookkeeping services step in.

Our team maintains your books of accounts continuously throughout the quarter rather than in a last-minute rush. We ensure your accounts are reconciled, figures are accurate, and your BAS is prepared well before the deadline, eliminating rushed receipt hunting and giving you complete peace of mind.

What happens if you miss the Q4 due date for BAS?

Missing the deadline can trigger a failure to lodge (FTL) penalty. Here is what you need to know:

• When it applies: if you had an obligation to lodge or report by a set date and did not meet it, including activity statements and tax returns.
• How you are notified: if the ATO decides to apply an FTL penalty, they will notify you in writing with the reason for the penalty, the amount, and a due date for payment that is at least 14 days out.
• How the penalty is calculated: based on the size of your business and how long the lodgement has been overdue, generally worked out in 28-day blocks, with larger businesses and withholders facing higher multiples.
• Isolated late lodgements: the ATO has said they do not usually apply penalties for a one-off late lodgement, and they will typically warn you by phone or in writing before issuing a penalty.
• Personal circumstances: if illness, family violence, or being affected by a disaster is getting in the way of lodging on time, these are situations the ATO has said they would likely consider for a penalty remission.
• Safe harbour with a registered agent: if you use a registered tax or BAS agent, safe harbour provisions may protect you from an FTL penalty, as long as you provided your agent with all the relevant information on time and the delay was not due to the agent's own conduct. This is one of the benefits of working with a registered agent rather than lodging solo.

What should you do if you cannot pay your BAS on time?

This is the part many business owners avoid, but the ATO's own guidance is clear: if you are finding it hard to lodge or pay in full and on time, contact them before the due date, not after. They will work with you to find a solution.

A few things to keep in mind:

1. Lodging and paying are two separate obligations. Lodging on time keeps your information current and gives you certainty about what you owe, even if you cannot pay the full amount straight away.
2. A general interest charge applies to anything unpaid after the due date. The sooner you sort out a plan, the less interest accrues.
3. A payment plan may be available if cash flow is tight. The ATO offers an online payment plan estimator so you can work out a realistic plan and see how quickly you could pay off the debt, along with an estimate of the interest involved.
4. It is still your responsibility, even with a tax agent. You, or your authorised representative or agent on your behalf, need to be the one reaching out to discuss your situation.

The earlier you engage, the more options tend to be available. This is exactly where having CleanSlate as your registered BAS agent helps, since we can flag potential cash flow issues early and talk to the ATO on your behalf if a payment plan or extension is the right path.

How often is BAS due in Australia?

A common question business owners ask is: how often is BAS due, and what months are BAS due throughout the year? Your reporting frequency depends on your annual GST turnover and ATO registration settings:

• Quarterly (Most Common): required for small and medium-sized businesses with a GST turnover under $20 million. The standard quarterly BAS due dates for self-lodgers fall on 28 October (Q1), 28 February (Q2), 28 April (Q3), and 28 July (Q4).
• Monthly: mandatory once your GST turnover reaches $20 million or more. Monthly activity statements are due on the 21st of every month following the reporting period.
• Annually: if you are voluntarily registered for GST and your turnover is under $75,000 ($150,000 for not-for-profit bodies), you can elect to report and pay GST annually. The standard due date to lodge and pay your annual GST return for the 2026–27 financial year is 31 October 2027. If you aren't required to lodge a tax return, then the due date is 28 February 2028. If you use a registered tax or BAS agent, different dates may apply.

Ready to hand over your Q4 BAS 2025–26?

Avoid last-minute deadline stress and secure an extended lodgement deadline of 25 August 2026. Our team handles your bookkeeping, account reconciliations, and direct ATO lodgements directly, so you can focus on running your business with total peace of mind. Book a call with our team today to get started.