BAS lodgement guide for Australia.

A Business Activity Statement reports GST, PAYG withholding and PAYG instalments to the Australian Taxation Office in one return. Most businesses lodge quarterly, with the September, December, March and June quarters due on 28 October, 28 February, 28 April and 28 July. Businesses turning over 20 million dollars or more lodge monthly.

What is a Business Activity Statement?

The BAS is a single form that settles several obligations at once. GST collected on sales and paid on purchases, tax withheld from employee wages under PAYG withholding, instalments toward your own income tax under PAYG instalments, and where relevant fuel tax credits, wine equalisation tax and luxury car tax. The ATO's guidance sits at business activity statements (BAS).

Because it bundles obligations, a BAS liability is rarely one number with one cause. A quarter that looks unaffordable is often a GST quarter that was always going to be large, sitting next to a PAYG instalment based on a prior year that no longer reflects the business. Those two problems have different fixes, and separating them is the first thing we do when a client says the BAS is too big.

Who has to register for GST, and when?

Registration is required once GST turnover reaches 75,000 dollars a year, or 150,000 dollars for a not-for-profit organisation. Taxi, limousine and ride-sourcing drivers must register from the first dollar of fare income regardless of turnover. You must register within 21 days of becoming aware that the threshold will be met, and registration requires an Australian Business Number first.

The test looks forward as well as back. If your current month plus the previous eleven reaches the threshold, or your current month plus the next eleven is likely to, you are required to register. A business that signs a large contract in July cannot wait until the following June to act on it. Registering late means the ATO can require GST on sales made since the date registration should have started, which comes out of margin because you never charged it.

The BAS lodgement guide for Australia: cycles and due dates

The December quarter already carries an extended date because of the holiday period. Lodging electronically through a registered BAS or tax agent attracts a further concession on several of the other quarters, which is worth real cash flow rather than just convenience. The concession applies to the lodgement channel, so it is lost if you file the quarter yourself after engaging an agent.

Cash or accruals: which GST basis should you use?

Businesses with an aggregated turnover under 10 million dollars can account for GST on a cash basis, reporting GST when money moves rather than when invoices are raised. Above that, accruals is required unless the ATO approves otherwise.

Cash basis suits businesses that invoice on long terms and get paid slowly, because you never remit GST on an invoice before the customer has paid it. Accruals suits businesses that pay suppliers on terms and collect from customers quickly, since the input credit is available at the invoice date. The choice is not permanent, but changing it requires an adjustment so the same transaction is neither taxed twice nor missed, and that adjustment is where most self-managed switches go wrong.

Small businesses under 10 million dollars also use Simpler BAS reporting, which asks for total sales, GST on sales and GST on purchases and drops the detailed export, input-taxed and capital purchase labels. Simpler BAS reduces the form, not the record keeping: you still need the underlying classification correct in your ledger, which is what our cloud bookkeeping service maintains and what MYOB accountants for Australian SMEs covers on the software side.

How do PAYG withholding and PAYG instalments work?

PAYG withholding is tax you take out of employee wages and remit. Your remittance cycle depends on the annual amount withheld: small withholders report quarterly on the BAS, medium withholders monthly, and large withholders on a twice weekly cycle. Growing past a threshold changes the cycle from the following period, and the ATO notifies you rather than asking.

PAYG instalments are prepayments of your own income tax, calculated by the ATO from your last assessed return. That is the crucial detail: a business whose profit has fallen is still being asked to prepay tax on last year's profit. You can vary an instalment down, but a variation that turns out to be more than 15 per cent below the eventual liability can attract a penalty, so vary on evidence rather than optimism.

Payroll reporting itself runs separately through Single Touch Payroll, which reports each pay run at the time it happens. STP and the BAS are two different pipes carrying related numbers, and where they disagree the ATO notices. Our multi-jurisdiction payroll service reconciles them each quarter, and the PAYE versus Form 941 comparison is useful if you also employ people in the UK or the US.

What about superannuation?

Super is not reported on the BAS, but it shares the quarterly rhythm and it is where the largest avoidable penalties sit. Super guarantee contributions are due by 28 October, 28 January, 28 April and 28 July, and the rate rose to 12 per cent of ordinary time earnings from 1 July 2025. The ATO's guidance is at super for employers.

Missing a super deadline is not like missing a BAS. Pay one day late and the deduction is lost, the superannuation guarantee charge applies on total salary and wages rather than ordinary time earnings, and a statement has to be lodged. Payday Super, which requires contributions to be made at the same time as salary rather than quarterly, is scheduled to commence on 1 July 2026, so confirm the current position with the ATO before setting next year's payroll calendar.

What happens if you lodge or pay late?

Failure to lodge on time is charged in penalty units, generally one unit for each period of 28 days a return is overdue, capped at five units for a small entity and multiplied for medium and large entities. The dollar value of a penalty unit is indexed, so check the current figure rather than an older one. On top of that, the general interest charge accrues daily on unpaid amounts, and from 1 July 2025 the general interest charge and the shortfall interest charge ceased to be deductible, which raised the real cost of carrying an ATO debt.

That deductibility change matters more than the headline rate. Financing a BAS liability with an ATO debt used to be partially subsidised by the deduction. It no longer is, which usually makes a commercial facility or simply paying on time the cheaper option. If you cannot pay, lodge anyway and arrange a payment plan: lodgement and payment are separate obligations, and lodging on time removes one penalty entirely.

A quarterly BAS process that holds up

1. Reconcile the bank and the clearing accounts first. An unreconciled undeposited funds account produces a GST figure nobody can defend.
2. Check GST coding on the awkward categories. Bank fees, government charges, insurance stamp duty, residential rent and overseas software subscriptions are the five that are routinely coded wrong.
3. Reconcile payroll to STP. Gross wages and withholding on the BAS should tie to the year-to-date STP figures, not approximately.
4. Review the PAYG instalment. Compare the ATO figure with actual year-to-date profit before accepting it.
5. Check the cash position against the liability before the 28th, not on it.
6. Lodge, then file the working papers with the return so the next quarter starts from an audit trail rather than a memory.

One opinion, from doing this quarterly: the businesses that struggle with BAS are almost never the ones with complicated GST. They are the ones treating GST collected as revenue. Move the GST portion of every receipt into a separate account on the day it lands, and the quarterly obligation becomes an administrative task instead of a cash event. It costs nothing and it changes the whole rhythm of the year.

Our accountants for Australian SMEs page sets out how we run the full ATO calendar, and VAT, GST and tax compliance covers the equivalent regimes across the other four markets. Businesses that have fallen several quarters behind should start with catch-up bookkeeping rather than lodging estimates. Terms used here are defined in our accounting and tax glossary, and the ATO publishes the current rates and dates.