The ATO has moved my BAS from quarterly to monthly — why, and can I change it back?

A letter arrives from the ATO, or your accountant mentions it almost in passing: from now on your BAS is monthly. Nothing about the business has changed — same turnover, same staff, same suppliers. And the July–September quarter was not due until late October anyway. Then you look at the date on the statement and it says 21 August. If that is roughly where you are sitting this week, the letter is not a system error and it is not random. It is a decision the ATO makes on grounds it publishes, and it comes with a process attached.

The three ways you end up reporting monthly

The first is size. If your GST turnover is $20 million or more you must report GST monthly, and you must lodge that BAS electronically through Online services for business. There is no choice in it.

The second is your own decision. If your GST turnover is less than $20 million you may choose to report monthly, and a fair number of businesses do — smaller and more frequent amounts are easier to keep on top of than one large quarterly bill.

The third is the one that arrives by letter. In the ATO's own words, where GST turnover is under $20 million, 'we may direct you to move to monthly reporting if you have a history of failing to comply with your tax obligations.' If you are nowhere near $20 million and you did not ask for this, that is the route you are on.

What the ATO says it is actually looking at

This started as a named campaign. In March 2025, as part of its 'Getting it right' campaign, the ATO notified 3,500 businesses with a history of non-compliance that they would be moved from quarterly to monthly GST reporting, effective 1 April 2025. The behaviours it listed are specific and unglamorous: paying late or not paying the amount due, not lodging or lodging late, and reporting tax obligations incorrectly. It also noted that these businesses had not responded to previous communications from the ATO — the letter is rarely the first contact.

Two details matter more than the campaign itself. The move applies for a minimum period of 12 months. And it is not a one-off exercise: the ATO's published position is that following the success of the campaign, it will continue to move businesses with a poor compliance history to monthly GST reporting where appropriate, as part of its broader compliance approach. In other words, this is now standing practice, not a 2025 event that has finished.

The ATO also publishes what came of it. As at March 2026, approximately a third of the businesses updated their registration details, approximately half were lodging and paying on time, and some recognised the need for additional support and registered with a new tax agent. Read plainly, that is the ATO saying the measure is working and it intends to keep using it.

The date that just moved on you

The due date to lodge and pay a monthly BAS is the 21st day of the month following the end of the taxable period. The ATO's own example is exactly the one in front of you: a July monthly BAS is due on 21 August. Where that date falls on a weekend or public holiday, you have until the next business day. In 2026, 21 August is a Friday.

Set that against the quarter you were used to. Quarter 1 — July, August and September — is due 28 October, and quarterly lodgers who lodge online may be eligible for an extra 2 weeks to lodge and pay, with further time possible through a registered tax or BAS agent. No equivalent two-week concession is published for monthly reporting. So the real change is not only twelve statements a year instead of four; it is that the first one falls about ten weeks earlier than the quarter would have, without the buffer you may have quietly been relying on.

The form itself is not necessarily heavier. If your GST turnover is less than $10 million you may report monthly using Simpler BAS, which means three labels: G1 total sales, 1A GST on sales, and 1B GST on purchases. But frequency has its own trap — even if you have nothing to report, you must still lodge a nil BAS by the due date.

Two things that get misread

The first is the belief that monthly means paying more tax. It does not. The GST rules, the rate and the amount payable across the year are unchanged; what changes is when it is reported and when it falls due — twelve instalments in place of four. What people are feeling is real, but it is a cash flow effect, not a tax increase. A business that had been treating the gap between quarters as an unofficial three-month buffer has just had that buffer removed, which is a different problem and needs a different fix.

The second is the belief that after twelve months it reverts by itself. Twelve months is a minimum, not an expiry date. Changing back is a request you have to make: a business or its registered agent can request a change of reporting and payment cycle through Online services for business or Online services for agents, while sole traders can do so through a registered agent, by contacting the ATO, or by applying in writing. It is also worth knowing that in the ATO's own published example — a carpentry business with 14 employees whose debt had reached $251,920 before it was moved to monthly in April 2025 — the business reached the end of its twelve months and chose to keep reporting monthly.

If you think the decision is wrong — and if you know it isn't

There is a review process. The ATO states that a review process is available for small businesses who don't believe they have a history of poor compliance and should be able to remain on their current GST reporting cycle, and that information about the review process, including objection rights, is provided to the business and its tax professional when the reporting cycle is changed. That makes the letter itself the document to keep rather than the one to throw out, and it makes the timing worth checking early rather than late.

If the decision is not wrong, the ATO's standing instruction is simple and often ignored: if you can't lodge or pay in full and on time, contact them before the due date. Its own worked example follows that path — when seasonal pressure hit in January 2026, the business asked for a deferral of its monthly BAS and the ATO approved the request under low-risk criteria. The request came before the date, not after it.

This is general information current as at August 2026 and not advice about your own situation — which route you are on, and what your options are, depends on your turnover, your lodgment history and what the letter actually says. The practical version: find the letter and read the review and objection information in it, put the 21st in the calendar as a recurring monthly date rather than something you notice each time, and be honest about which underlying problem you are solving. If the issue is that the money isn't there, that is a payment conversation with the ATO and it goes better before a due date than after one. If the issue is that the bookkeeping is behind, monthly reporting will multiply that by three — twelve statements a year on messy books is twelve times the work, and getting the records clean first is what our business accounting and bookkeeping service is built around.