The 2026 BAS calendar comes down to a few dates worth memorising.
Quarterly lodgers: 28 January, 28 April, 28 July, and 28 October 2026. Monthly lodgers: the 21st of the following month. Two of those monthly dates shift in 2026 because the 21st lands on a Sunday, May’s BAS rolls to Monday 22 June, and November’s rolls to Monday 22 December. If you’ve got a registered BAS agent, you usually get an extra four weeks on the quarterlies. Usually, the June 2026 quarter is the exception, and that one trips people up every year.
Lodge late and the ATO charges $313 for the first 28 days. Stay late, and it climbs in $313 increments, $626, $939, $1,252, capped at $1,565 for small entities. If you owe money on top of that, General Interest Charge runs daily at around 11% a year until the debt’s paid off. Below: the full 2026 calendar, the agent concession quirks, the labels that catch most businesses out, and the reconciliation work that runs before every lodgement.
The 2026 quarterly BAS calendar
Most Melbourne small businesses lodge quarterly. If your GST turnover is under $20 million, that’s almost always your cycle. The standard due date is the 28th of the month after each quarter ends, and a weekend or national public holiday automatically pushes it to the next business day.
Registered BAS or tax agents lodging electronically get a concession on top. Four weeks for the December and March quarters. Less for the others.
| Quarter | Period | Standard due | Agent concession |
| Q2 2025-26 | 1 Oct – 31 Dec 2025 | 28 Jan 2026 (Wed) | 25 Feb 2026 |
| Q3 2025-26 | 1 Jan – 31 Mar 2026 | 28 Apr 2026 (Tue) | 26 May 2026 |
| Q4 2025-26 | 1 Apr – 30 Jun 2026 | 28 Jul 2026 (Tue) | 11 Aug 2026 |
| Q1 2026-27 | 1 Jul – 30 Sep 2026 | 28 Oct 2026 (Wed) | 25 Nov 2026 |
Look at the Q4 row. The agent concession date is 11 August, a Tuesday, only 14 days after the standard 28 July deadline. Most clients assume four weeks. They get two. Diarise it now, or August becomes a scramble.
The 28 January 2026 date sits two days after Australia Day. No extension, because the deadline already falls after the public holiday. Worth being aware of, the long weekend can lull you into thinking there’s more room.
The 2026 monthly BAS calendar
Monthly BAS is mandatory once your GST turnover hits $20 million. It’s also a sensible voluntary choice for some hospitality operators with high GST throughput, tradies with apprentices and subbies pushing PAYG withholding over $25,000 a year, and anyone who wants smaller, more frequent payments to smooth out cash flow.
Monthly lodgers don’t get an agent concession. The 21st is the deadline, with weekend and holiday shifts handled automatically by the ATO.
| Reporting month | Due date |
| December 2025 | 21 Feb 2026 (Christmas extension) |
| January 2026 | 21 Feb 2026 |
| February 2026 | 21 Mar 2026 |
| March 2026 | 21 Apr 2026 |
| April 2026 | 21 May 2026 |
| May 2026 | 22 Jun 2026* |
| June 2026 | 22 Jul 2026* |
| July 2026 | 21 Aug 2026 |
| August 2026 | 21 Sep 2026 |
| September 2026 | 21 Oct 2026 |
| October 2026 | 23 Nov 2026* |
| November 2026 | 22 Dec 2026* |
| December 2026 | 22 Feb 2027 (Christmas extension) |
*Shifted to the next business day because the 21st falls on a weekend.
Two things on this calendar deserve flagging.
The Christmas extension. Sounds generous. It isn’t really, because the December BAS gets pushed to 21 February and the January BAS lands on the same day. Two months of GST and PAYG hitting one date. If your monthly liability normally runs at $20,000, you need $40,000 in the account by late February. This catches businesses every single year.
The 22 June and 22 December shifts. Both Mondays. If the calendar still has the 21st locked in by default, update it now.
The agent concession trap
The BAS Agent Lodgment Program sits under section 162-5 of the Taxation Administration Act 1953. In plain terms, it gives the Commissioner of Taxation the discretion to defer due dates for clients of registered agents. For most quarters, that’s four extra weeks.
The June quarter isn’t most quarters.
The 2026 program compresses the Q4 window down to 14 days, which is why the concession ends on 11 August. The December and March quarters still get the full four weeks. The June one doesn’t. Anyone used to a comfortable buffer between 28 July and the agent’s lodgement date will find the gap shorter than expected. Plan reconciliations earlier.
Two other things worth knowing about the concession:
You need to be on the agent’s client list with electronic lodgement access before the previous BAS is lodged. New clients sometimes assume the concession kicks in automatically in the first quarter they engage bookkeeping services. It often doesn’t.
Q2 doesn’t get a separate agent extension on top of the standard 28 February deadline. The one-month buffer’s already built in.
Annual GST reporting (and why it suits very few businesses)
Voluntarily registered for GST with turnover under $75,000, or under $150,000 if you’re a not-for-profit? You can elect to lodge an Annual GST Return instead of a quarterly or monthly BAS. The due date matches your income tax return, so 31 October if you’re self-preparing, or later through a registered tax agent.
The annual option works for a narrow group. Investors holding a single commercial property. Sole traders with low transaction volumes. Some not-for-profits are running below the threshold. For most operating businesses in Melbourne, the cash flow benefit of getting GST refunds quarterly outweighs the simplicity of an annual return.
What’s on the BAS itself
The form’s shorter than people expect. The labels carry weight, though, and most BAS queries from the ATO trace back to a mismatch on one of them.
Labels 1A and 1B — GST. 1A is GST collected on sales. 1B is GST paid on purchases. Both have to reconcile to the GST report in your accounting software for the period. Not approximately. Exactly.
Labels W1 and W2 — PAYG withholding. W1 is gross wages. W2 is the tax withheld from those wages. This is where most payroll-related BAS errors surface. W2 has to equal your STP year-to-date withholding for the same period. If those figures don’t match, the gap’s almost always a payroll timing issue or a misallocated pay run, not a BAS problem. Find the cause before lodging, not after a letter from the ATO.
Labels T7 and T8 — PAYG instalments. Pre-paid income tax instalments. If income’s dropped, you can vary T7 or T8 down through ATO Online Services before the due date. The catch is that downward variations need a reasonable basis. Vary too aggressively, and you face underpayment penalties at year’s end.
Labels 5 and 5A — wine equalisation tax and fuel tax credits. Industry-specific. Fuel tax credits matter for trades, transport and primary production. WET applies to wine producers and wholesalers.
Not every label appears on every BAS. You only see the ones tied to your registration.
The reconciliation work that stops ATO queries
A clean BAS isn’t about lodging fast. It’s about lodging once, correctly. The pre-lodgement work takes 30 to 60 minutes for most small businesses. Skip it, and you create problems that take days to unwind.
This is the run-through that should happen before any lodgement:
1. All transactions coded
Every sale, expense, bank transaction and invoice for the period entered and coded properly in Xero, MYOB or QuickBooks. Uncoded items distort GST and PAYG.
2. GST method matches the ATO registration
Cash or accrual. The software setting needs to match what the ATO has on file. Mismatches create timing differences that look like errors.
3. W2 reconciled to STP year-to-date
Pull the STP YTD figure for the period. Compare it to W2. They should match. Round-dollar gaps usually mean a pay run was processed in the wrong period.
4. PAYG instalment reviewed
Income shifted? Decide whether T7 or T8 needs to vary. Document the reason.
5. Nil BAS prepared if it applies
No activity doesn’t mean no lodgement. Failure to Lodge applies to a nil BAS the same way it applies to any other.
6. BAS preview run
In Xero, that’s the BAS Preview report. In MYOB, the GST Detail report. Look for uncoded transactions, unusual GST balances, and negative PAYG.
7. Reconciliation reports saved
Every variance is documented. Every report is archived. If the ATO queries the lodgement later, the audit trail’s already there.
This is the part most businesses get wrong, and it’s the difference between a 10-minute lodgement and a six-week back-and-forth with the Tax Office.
What happens when you lodge or pay late
Two penalty mechanisms, and they stack.
Failure to Lodge
Applied automatically when the BAS sits overdue. One penalty unit currently equals $313, and the ATO charges a unit per 28 days (or part of) up to a five-unit cap. The math for small entities:
| Days late | Penalty units | Amount |
| 1–28 | 1 | $313 |
| 29–56 | 2 | $626 |
| 57–84 | 3 | $939 |
| 85–112 | 4 | $1,252 |
| 113+ | 5 | $1,565 |
Medium entities (assessable income over $1 million) double the penalty. Large entities (over $20 million) multiply by five.
General Interest Charge
Applied to any unpaid amount. Daily compounding. The rate sits around 11% a year, published quarterly by the ATO. GIC keeps running until the full liability, including the GIC itself, is paid off.
Director Penalty Notices
This is the one most company directors don’t know about until it happens. Under the DPN regime, directors can be made personally liable for unpaid PAYG withholding and Super Guarantee. The Pty Ltd structure doesn’t protect them. Sole traders aren’t affected because there’s no separate legal entity, but anyone running through a company should treat PAYG and super as personally guaranteed obligations.
The rule that actually matters: lodge on time even if you can’t pay. Failure to Lodge is triggered by late lodgement, not late payment. If cash flow’s tight, lodge by the deadline and call the ATO to set up a payment plan. GIC will still accrue on the unpaid balance, but it avoids the bigger FTL hit and demonstrates good faith, which the Commissioner takes into account when assessing remission later.
Already missed a deadline? Lodge immediately through ATO Online Services or your agent, then call the ATO business line before they call you. Voluntary disclosure usually reduces penalty severity.
When it’s worth bringing in a registered BAS agent
The honest answer: not always.
Some businesses run lean enough that a self-prepared BAS in Xero or MYOB works fine. The point at which it stops working is usually one of three triggers.
You’ve started employing staff, and W1, W2 and the corresponding STP year-to-date figures need to reconcile cleanly every quarter. A misallocated pay run that took ten minutes to create now takes hours to unwind.
You’ve had an amendment or two. The ATO flagged a discrepancy or asked you to vary an instalment, and the reasonable basis required for a downward T7 or T8 variation isn’t something you want to guess at.
You’re spending time on BAS that should be in the business. The fee for outsourced bookkeeping rarely exceeds the cost of the time lost reconciling at midnight before a deadline, plus the risk of getting the timing wrong.
When a new client comes on board, the first piece of work is usually reconciling the last four BAS lodgements against STP and the GST report. About half the time, there’s a small variance worth correcting. That’s not a criticism; it’s what happens when you’re running a business and doing the books between everything else.
If your books feel like a problem you keep pushing back, that’s usually the right time to bring someone in.
Frequently asked questions
When is BAS due in 2026?
Quarterly BAS for the 2025-26 income year is due 28 January 2026 (Q2), 28 April 2026 (Q3) and 28 July 2026 (Q4). Q1 of 2026-27 is due 28 October 2026. Monthly BAS is due the 21st of the following month, with the December activity statement extended to 21 February under the Christmas concession. Registered BAS agents receive lodgement extensions on most quarterly lodgements through the BAS Agent Lodgment Program.
Do I have to lodge a BAS if I had no activity?
Yes. A nil BAS is still a BAS. Failure to lodge applies whether you owe money or not. Silence isn’t a lodgement.
What’s the difference between a BAS agent and a tax agent?
A BAS agent is registered with the Tax Practitioners Board to provide BAS services. That covers preparing and lodging activity statements, plus advising on GST, PAYG withholding, fuel tax credits and other indirect taxes. The framework sits under the Tax Agent Services Act 2009. A tax agent has broader authority, the same BAS work, plus income tax returns, company tax, and the full spectrum of tax law. Plenty of firms hold both registrations.
What happens if I can’t pay my BAS on time?
Lodge by the deadline regardless. Failure to Lodge is tied to lodgement, not payment. Once it’s in, call the ATO to arrange a payment plan. GIC will keep accruing on the unpaid balance at around 11% a year, but it avoids the much larger FTL penalty and demonstrates good faith, which matters when the Commissioner considers remission later.
Why are December and January BAS due on the same day?
The ATO grants a Christmas extension on the December monthly BAS, pushing it from 21 January to 21 February (or the next business day). The January BAS already sits on 21 February. So monthly lodgers cop two months of GST and PAYG falling due simultaneously. Plan cash flow for late February now, not when the deadline arrives.
Can I switch from quarterly to monthly BAS reporting?
You can switch, but there are limits. The ATO allows one change a year, and the request needs to go in before the start of the new tax period. So if you want monthly reporting from 1 July 2026, get the application in by 30 June. Worth knowing, the ATO can also force you onto a monthly payment regardless of preference, usually if your PAYG withholding is over $25,000 a year or your GST obligations aren’t being met. Update the cycle setting in Xero, MYOB or QuickBooks once the change is approved.
Get your BAS sorted before the next deadline
If your books feel like a quarterly scramble, the system needs work, not you. We work with Melbourne small businesses across hospitality, trades, retail, healthcare and professional services to keep BAS lodgements clean, on time, and lined up with cash flow rather than fighting against it.
Contact us about your BAS and bookkeeping.
