The four dates
Quarterly activity statements are generally due on the 28th of the month after the quarter ends — with one exception, which exists because the December quarter runs through the holidays.
| Quarter | Period | Due | Extra 2 weeks if you lodge online? |
|---|---|---|---|
| Q1 | 1 July – 30 September | 28 October | May apply |
| Q2 | 1 October – 31 December | 28 February | No — this date already includes a month's extension |
| Q3 | 1 January – 31 March | 28 April | May apply |
| Q4 | 1 April – 30 June | 28 July | May apply |
Source: the ATO's BAS due dates, read August 2026. Lodging through a registered tax or BAS agent may also give you a later date. Check the current page for your own situation.
The three boxes
Small businesses with a GST turnover under $10 million report under Simpler BAS, which cut the GST section down to three labels. If someone shows you a BAS form covered in codes, that is the full version — most tradies never see it.
| Label | What it is | Where it comes from |
|---|---|---|
| G1 | Total sales for the quarter, including GST | Every invoice you issued (or were paid on — see cash vs accrual below) |
| 1A | GST on sales — what you collected | Generally one eleventh of your GST-inclusive sales |
| 1B | GST on purchases — what you can claim back | The GST on business purchases you hold a tax invoice for |
1A minus 1B is what you pay. If 1B is bigger — a quarter where you bought a ute or a lot of stock — the ATO refunds the difference. There are two other sections you may see: PAYG withholding (only if you have employees) and PAYG instalments (prepayments toward your own income tax, if the ATO has entered you into the system).
A worked quarter
A sole-trader sparky, registered for GST, cash basis, first full quarter. Every number here is derived so you can follow it with your own figures.
What came in
| Month | Money received (inc GST) |
|---|---|
| July | $18,700.00 |
| August | $24,200.00 |
| September | $21,450.00 |
| G1 — total sales | $64,350.00 |
1A — GST on sales = $64,350 ÷ 11 = $5,850.00
What went out (business purchases with GST)
| What | Paid (inc GST) | GST in it |
|---|---|---|
| Materials from the wholesaler | $16,940.00 | $1,540.00 |
| Fuel | $2,090.00 | $190.00 |
| Tools and consumables | $3,410.00 | $310.00 |
| Phone, software, accounting | $1,155.00 | $105.00 |
| Insurance (public liability) | $1,320.00 | $120.00 |
| 1B — GST on purchases | $2,265.00 |
The answer
| 1A GST on sales | $5,850.00 |
| 1B GST on purchases | −$2,265.00 |
| Net GST payable | $3,585.00 |
That is the whole BAS. Due 28 October for this quarter. Note what it is not: it is not the sparky's income tax, which is worked out on profit at the end of the financial year and is a separate, usually larger, number.
The pre-lodgment checklist
- Every invoice for the quarter is entered, including the cash jobs. Undeclared cash is the fastest way to turn a routine BAS into a problem.
- Decide which basis you are on — cash or accrual. It changes which invoices belong in this quarter. See cash vs accrual GST.
- You hold a tax invoice for every GST amount you are claiming at 1B.
- Private use is taken out. The half of the phone bill that is personal, the ute's private kilometres — only the business share is claimable.
- Big purchases checked. A vehicle or a large tool purchase can swing the quarter into a refund, and there are separate rules for cars worth knowing about before you claim.
- 1A and 1B sanity check. 1A should be very close to G1 ÷ 11 if all your sales are taxable. If it is not, something is misclassified.
- Lodge on time even if you cannot pay. See below.
If you cannot pay it
Lodge anyway, on time. Lodging and paying are two separate obligations, and a late lodgment can attract a failure-to-lodge penalty on top of interest on the unpaid amount. Then contact the ATO about a payment plan — they are set up for this, small businesses use them routinely, and the conversation is much easier before the due date than after it. Talk to your accountant or a registered BAS agent if you are not sure how to approach it.
Cash or accrual — the one decision that changes the numbers
On a cash basis the GST follows the money: you report the GST when you are paid. On an accrual basis it follows the invoice: you report it in the quarter you invoiced, even if the customer has not paid. For a tradie who invoices at the end of a job and waits thirty days for payment, that difference decides whether you are paying GST on money you have not yet received. Businesses under $10 million turnover can generally choose. It is worth ten minutes: cash vs accrual GST, with timelines.
See your GST as you earn it — Yamate keeps the numbers current →Yamate tracks the GST on every invoice as you raise it and every expense as you record it, so G1, 1A and 1B are a screen rather than a shoebox in October. It is an estimate to prepare from — Yamate does not lodge your BAS and it is not tax advice; you lodge it yourself or through your agent. Sign up before 30 September 2026 and lock in the Founder plan at $19/mo — forever. It's $29/mo after that. No lock-in, cancel anytime. Prices in AUD.
FAQ
When is my quarterly BAS due?
Generally the 28th of the month after the quarter ends — 28 October, 28 February, 28 April and 28 July. Lodging online may give an extra two weeks on some quarters, but not the December quarter, whose date already includes a month's extension.
What goes on a Simpler BAS?
Three GST labels — G1 total sales, 1A GST on sales, 1B GST on purchases — for businesses with GST turnover under $10 million. Add PAYG withholding if you have employees, and PAYG instalments if the ATO has entered you into that system.
Is the GST on my BAS the same as my tax?
No. GST is money you collected for the ATO and never owned. Income tax is worked out separately on your profit at the end of the year — see how much tax to put aside.
What if I can't pay?
Lodge on time regardless, then contact the ATO about a payment plan. Lodging late can attract its own penalty on top of the interest.
Do I need an accountant for it?
Not necessarily — a Simpler BAS with clean records is three numbers. Many tradies use a registered BAS or tax agent for the first one to check the setup is right, and an agent may have access to a later lodgment date.
What if I made a mistake on a BAS I already lodged?
Most small errors can be corrected on a later BAS, and larger ones through a revision. The ATO publishes the thresholds for which route applies — check them, or ask your agent, rather than leaving it.
Related
General information for Australian businesses, not tax advice. Yamate does not lodge your BAS, does not hold or pay your tax, and every figure here is an estimate. Your circumstances, your basis of accounting and the current ATO rules all change the answer — check the ATO's BAS guidance or talk to your accountant or a registered BAS agent. This page describes the position as read in August 2026.