The September quarter BAS is due on 28 October 2026 if you lodge it yourself. If a registered BAS agent lodges it for you, the ATO’s lodgment program in most cases extends that to 25 November 2026. That four-week gap is the most useful thing to know this month. The second most useful is what it costs to lodge late, or not at all.
This article covers the dates and the agent concession, including who qualifies for it. It then covers what a late BAS costs and what “catching up” involves when the books are not ready to lodge from.
When is the Q1 BAS due in 2026?
For quarterly lodgers, the first quarter of the 2026-27 year (July to September) is due on 28 October 2026. The remaining quarters follow the usual pattern: Q2 (October to December) is due 28 February 2027, Q3 (January to March) on 28 April 2027 and Q4 (April to June) on 28 July 2027. Monthly lodgers report by the 21st of the following month.
If a due date falls on a weekend or public holiday, the ATO accepts lodgment and payment on the next business day. In 2026, 28 October is a Wednesday, so the date stands.
The BAS agent concession
Registered BAS agents and tax agents lodge under the ATO’s lodgment program, which gives most of their quarterly clients extra time. For Q1 the agent date is 25 November 2026, and for Q3 it is 26 May 2027. Q2 is the exception: the December quarter carries an extended due date of 28 February for all lodgers, so there is no further agent concession. The ATO publishes Q4’s agent date in the lodgment program each year.
Three conditions apply. The agent must hold registration with the Tax Practitioners Board, and you must be on their client list with the ATO before the original due date; the concession does not rescue a statement that was overdue before the agent took you on. The extra time covers lodgment and payment together, so cash flow moves with it. And the concession is the agent’s to use, which means a business that hands over its file on 24 November has used up the four weeks the agent needed to prepare it.
What a late BAS actually costs
Two things happen when a BAS is late. The ATO can apply a failure to lodge on time penalty, calculated in penalty units for each 28-day period or part of one that the statement is overdue, up to a maximum number of periods and scaled up for medium and large entities. On top of that, any amount you owe accrues the general interest charge from the original due date until you pay it, whether or not the ATO applies a penalty.
The less visible cost is your standing. The ATO treats a business with a lodgment gap as a different case from one that lodges on time and pays late, and that shapes how it receives payment arrangements and remission requests. Lodging on time, even when you cannot pay in full, keeps the conversation about money rather than compliance.
“Behind on your books” is the usual reason
Most late BASs are late because the books are not reconciled. Few are late because anyone forgot the date. A BAS is only as good as the ledger it comes from. If the bank feeds are months behind and the GST codes are guesses, and if payroll does not reconcile to the wages account, you cannot prepare the statement with confidence, so it slides. Our view is blunt: a BAS prepared from unreconciled books is a guess with a signature on it.
Catching up is a defined piece of work, in this order:
- Reconcile each bank and card account to the statement date.
- Review the GST coding on the transactions that matter (large purchases, capital items, anything international).
- Reconcile PAYG withholding to the figures reported through Single Touch Payroll.
- Only then prepare the statement.
For a business that is one or two quarters behind, that is days of work rather than weeks, and a fixed-fee bookkeeping package keeps it from recurring.
What a registered BAS agent does with your BAS
Preparing and lodging a BAS for a fee is a BAS service under the Tax Agent Services Act 2009, and only a registered agent can provide it. In practice a registered BAS agent reconciles GST and PAYG withholding before anything goes in, then shows you the figures and what they mean. The agent lodges under the agent program and deals with the ATO on your behalf if a query or a payment arrangement comes up. The reconciliation is the part that matters. An error caught before lodgment is a correction; an error the ATO finds in a review is an amendment with interest.
What to do this month
- Confirm your lodgment method and date. Self-lodging means 28 October. Through a registered agent who has you on their list, 25 November.
- Check the books reconcile to 30 September. If they do not, that is the job for the next fortnight, not the day before the deadline.
- Plan the payment. The GST and PAYG withholding you have collected since July are not your money. If that money has gone, a payment arrangement is far easier to agree before the due date than after it.
- Lodge on time even if you cannot pay in full. The penalty is for not lodging; the interest is for not paying. They are separate problems, and the first one is avoidable.
Frequently asked questions
Can I get the agent extension if I appoint a BAS agent now?
For Q1, yes in most cases, provided the agent registers you as a client with the ATO before 28 October 2026 and the statement is not overdue at that point. Leaving it until the last week gives the agent no time to prepare the statement with care, which defeats the purpose.
What if I lodge on time but cannot pay?
Lodge anyway. You avoid the failure-to-lodge penalty, and the amount owing accrues the general interest charge until you pay it. The ATO offers payment arrangements, and a registered agent can set one up on your behalf.
I have not lodged for several quarters. Where do I start?
With the oldest quarter, and with the books rather than the forms. Reconcile the accounts first. Then prepare the statements in order and lodge them together; where it fits, your agent can request remission of penalties with the lodgments.
Does the 28 February Q2 date get extended for agents?
No. The December quarter carries an extended due date for all lodgers, so the agent program does not add to it.
If your September quarter is not ready, or you want it lodged by a registered agent with the extra time that brings, book a discovery call at ascendsolutions.com.au/contact or phone (02) 6189 2248.
