Do I have to lodge BAS if I’m not registered for GST?

No. BAS only applies once you’re registered for GST. If your turnover is under $75,000 and you’re not registered, you don’t lodge BAS — your income tax return covers your reporting obligations.

Can I lodge BAS myself or do I need an accountant?

Either works. For a simple sole-trader BAS with straightforward income and expenses, lodging yourself via myGov or ATO Online Services takes 15–30 minutes. Complex businesses, mixed GST, or multi-state issues are usually worth handing to a BAS or tax agent.

What happens if I lodge BAS late?

The ATO can apply Failure to Lodge (FTL) penalties — currently $222 per 28 days late, capped at five units ($1,110) for small businesses. Late payment also accrues general interest charges (GIC) on the unpaid amount. Even if you can’t pay, lodging on time avoids the lodgement penalty.

Do I report cash basis or accruals basis on BAS?

Sole traders with turnover under $10 million can choose either. Cash basis (most common for sole traders) reports GST on the date money actually changes hands. Accruals reports GST on the invoice date regardless of payment. Pick one and stick with it — the ATO needs consistency.

How to Prepare for BAS in Australia (Sole Trader Quarterly Guide)

Q: When is BAS due each quarter?

Standard ATO due dates are: Q1 (Jul–Sep) due 28 October; Q2 (Oct–Dec) due 28 February; Q3 (Jan–Mar) due 28 April; Q4 (Apr–Jun) due 28 July. If you lodge through a registered tax or BAS agent, the deadlines are typically extended by 4 weeks.

Quick answer

To prepare a quarterly BAS in Australia: total the GST collected on your sales invoices for the quarter, total the GST paid on your business expenses for the same period, and report the difference to the ATO. If you collected more GST than you paid, the difference is owed to the ATO. If you paid more than you collected, you get a refund. Quarterly BAS is due 28 days after the quarter ends (28 Oct, 28 Feb, 28 Apr, 28 Jul).

Note: this is general information, not tax advice. Refer to ato.gov.au or your tax/BAS agent for guidance on your specific situation.

Do you actually need to lodge BAS?

BAS is only required if you’re registered for GST. You must register for GST if:

Your GST turnover is $75,000 or more in any 12-month period, OR
You drive a taxi or ride-share (Uber, DiDi, etc.) — required from day one, OR
You’ve voluntarily registered even though under the threshold

If none of the above apply, you don’t need to lodge BAS. Your income tax return covers your annual reporting. See how to invoice without GST for what your invoices should look like in that case.

The 5-step BAS preparation workflow

Step 1: Confirm your reporting period

Most sole traders lodge BAS quarterly. Some larger businesses lodge monthly, and very small ones can apply for annual. Quarterly periods follow the financial year:

Q1: 1 July — 30 September
Q2: 1 October — 31 December
Q3: 1 January — 31 March
Q4: 1 April — 30 June

Step 2: Total your GST collected (G1 + 1A)

Add up the GST you charged on every invoice issued in the quarter. If you use cash basis accounting (most sole traders), count invoices paid in the quarter, not just issued. If you use accruals, count invoices issued in the quarter regardless of payment status.

For each invoice, you need:

Total sales amount (label G1 on the BAS form)
GST on those sales (label 1A)

If you exported some services overseas (GST-free), include the total in G1 but report it separately at label G3 — export sales don’t add to 1A. See how to add GST to invoices for the calculation rules.

Step 3: Total your GST paid (G11 + 1B)

Add up the GST you paid on every business expense in the quarter. This is the credit (“input tax credit”) you claim back. For each expense:

Total purchase amount (label G11)
GST in that purchase (label 1B)

Only expenses with a valid tax invoice from a GST-registered supplier count. Receipts from non-GST suppliers (e.g. a sole trader under $75k) have no GST credit. Receipts under $82.50 don’t require a full tax invoice but you still need evidence.

For the categories and evidence rules, see how to track business expenses.

Step 4: Calculate net GST

Net GST = 1A (collected) − 1B (paid). Two outcomes:

Positive number: you owe the ATO. Set this amount aside the moment each sale lands. Treat it as the client’s money you’re holding, not yours.
Negative number: the ATO owes you a refund (this is normal for low-sales quarters where capital purchases dominate).

Step 5: Lodge by the deadline

Lodgement options:

myGov / ATO Online Services for sole traders. Free, takes 15–30 minutes once your numbers are ready.
Through a registered BAS agent or tax agent. They get a 4-week extension on the deadline as a concession, which is useful if quarterly timing is tight.
Compatible SBR software. Some accounting packages lodge directly.

Pay any amount owed via BPAY, direct debit, or credit card on the same screen. If you can’t pay in full, lodge anyway — you can request a payment plan separately, but late lodgement attracts a separate penalty.

Cash basis vs accruals basis

A sole trader with turnover under $10 million can elect either:

Cash basis (most common): GST is reported when money actually changes hands. Simpler — matches your bank statements. Default for most sole traders.
Accruals basis: GST is reported on the invoice date. Slightly more complex but matches accounting standards more closely.

Once you elect a method, the ATO expects consistency. Switching mid-year requires written notification.

What you actually need to collect

The good news: BAS doesn’t require you to send the ATO any of the underlying documents. You just need to be able to produce them on request for the next 5 years. Keep:

Every sales invoice issued in the quarter (digital is fine)
Every tax invoice or receipt for business expenses with GST
Bank statements for the quarter
A summary spreadsheet or report showing the totals you reported

See how long to keep invoices for the full retention rules.

The mistakes that cost time at BAS

Letting categorisation slip. Uncategorised expenses pile up and quarterly BAS becomes a re-sorting marathon.
Mixing personal and business spend on the same card. Apportioning line-by-line at quarter end is brutal.
Forgetting the GST on payment processor fees. Stripe and similar fees usually include GST — that’s a credit you’re owed.
Not setting aside GST as it’s collected. The client’s GST money isn’t yours. A separate sub-account avoids cash-flow surprises at lodgement.
Lodging late. $222 per 28 days, compounding. Even an empty BAS is cheaper to lodge on time than late.

How Free Invoice App helps

Free Invoice App tracks GST per invoice and per expense automatically. The revenue and profit-and-loss reports let you pull totals for any date range — including the exact quarter dates for BAS. Export the period summary, copy the totals into your BAS form, and you’re done. Every invoice and expense record stays in your account well beyond the 5-year ATO requirement. Get started free — revenue and P&L reports are included on the Starter plan.

Frequently asked questions

When is BAS due each quarter?

28 October, 28 February, 28 April, 28 July. Add 4 weeks if you lodge through a registered tax or BAS agent.

Do I have to lodge BAS if I’m not GST-registered?

No. BAS only applies once you’re registered. Your income tax return covers reporting if you’re not.

Can I lodge BAS myself?

Yes — via myGov or ATO Online Services. Most simple sole-trader BAS lodgements take 15–30 minutes once the totals are ready.

What happens if I lodge late?

$222 per 28 days late, capped at $1,110 for small businesses. Plus general interest charges on any unpaid amount. Always lodge on time, even if you can’t pay yet.

Cash basis or accruals?

Cash is most common for sole traders. Pick one and stay consistent.