How do I lodge a BAS (Business Activity Statement) in Australia?
You lodge a BAS online through myGov or the ATO Business Portal, by mail, or through a registered BAS or tax agent. Most small businesses lodge quarterly, with the statement due 28 days after the end of each quarter.
Detailed Explanation
The Business Activity Statement (BAS) is the core compliance document for GST-registered businesses in Australia. It reports your GST collected on sales, GST credits claimed on purchases, PAYG withholding amounts, PAYG instalments, and other tax obligations. Understanding how to prepare and lodge a BAS accurately is essential to staying compliant with the ATO.
Who needs to lodge a BAS?
Every business registered for GST must lodge a BAS. If you are only registered for PAYG withholding (for example, you pay wages but are not GST-registered), you may receive an Instalment Activity Statement (IAS) instead. The BAS combines multiple tax obligations into one form.
BAS lodgement frequency
The ATO assigns your BAS reporting cycle based on your annual turnover: - Monthly: Businesses with GST turnover of $20 million or more must lodge monthly. - Quarterly: Most small businesses with GST turnover under $20 million are assigned quarterly lodgement. - Annually: Businesses with GST turnover under $75,000 that voluntarily registered for GST may be eligible for annual lodgement with quarterly PAYG instalments.
You can elect to lodge monthly even if you are below the threshold, which can improve cash flow visibility.
BAS due dates: quarterly cycle
The four standard quarterly BAS periods and due dates are: - Quarter 1 (July-September): due 28 October - Quarter 2 (October-December): due 28 February (extended) - Quarter 3 (January-March): due 28 April - Quarter 4 (April-June): due 28 July
BAS agents receive a lodgement program that typically extends these deadlines by 4 weeks, so using a BAS agent provides additional time.
What to report on your BAS
The BAS has several sections depending on your registrations:
GST section: - G1: Total sales (all income including GST) - G2: Export sales (GST-free) - G3: Other GST-free sales - G10: Capital purchases - G11: Non-capital purchases - 1A: GST on sales (output tax) - 1B: GST credits (input tax credits on purchases)
The net GST payable or refundable is 1A minus 1B. If 1B exceeds 1A, you receive a refund.
PAYG withholding: If you employ staff, W1 reports total wages paid and W2 reports the total PAYG withholding deducted from wages. This is separate from your GST liability.
PAYG instalments: If you are self-employed or have business income, the ATO may require quarterly PAYG instalment payments (T7) toward your annual income tax liability.
How to lodge
There are three main ways to lodge: 1. Online through myGov: Link your myGov account to the ATO and lodge through the Business Portal. 2. Through accounting software: Cloud software pre-fills the BAS from your transaction data and allows direct lodgement to the ATO via SBR. 3. Through a registered tax or BAS agent: A BAS agent handles preparation and lodgement and receives extended due dates.
Paying your BAS
Payment is due on the same date as lodgement. Payment options include BPAY, direct debit, EFT, credit or debit card, or cheque by mail. If you cannot pay in full, contact the ATO before the due date to discuss a payment plan.
GST accounting methods
There are two methods for calculating GST on your BAS:
Accruals method: Report GST when you issue an invoice (for sales) or receive a bill (for purchases), regardless of when payment is received. This is the default method.
Cash method: Report GST only when payment is actually received or made. This method is better for cash flow and requires ATO approval; available if turnover is under $10 million.
Correcting errors on a previous BAS
If you made a mistake on a previous BAS, you can correct it on your next BAS if the error is under the relevant threshold ($10,000 for annual turnover under $20 million). For larger errors, you must revise the original BAS or contact the ATO. You have four years from the original lodgement date to amend a BAS.
Penalties for late lodgement
The ATO charges failure-to-lodge (FTL) penalties for late BAS. As of 2024-25, the penalty is $313 per 28-day period the BAS is overdue, up to a maximum of $1,565 for small businesses. Late payment also attracts the general interest charge (GIC).
Source: ATO Business Activity Statements
Real-World Examples
Quarterly BAS for a tradie
A plumber earned $55,000 (ex-GST) in Q1 (July-September) and paid $8,800 in GST-inclusive supplies. Their BAS shows: GST collected ($5,500) minus GST credits ($800) = $4,700 net payable to ATO. Plus PAYG withholding for one employee. Total BAS due 28 October.
GST refund quarter for a retailer
A retail business had a slow sales quarter but purchased $50,000 in stock (including $4,545 GST). They only sold $20,000 (including $1,818 GST). Their input tax credits exceed their output tax: $4,545 - $1,818 = $2,727 refund. The ATO deposits this within 14 days of lodgement.
Common Mistakes to Avoid
- Reporting G1 total sales as the GST-exclusive amount rather than GST-inclusive — G1 should always be the total including any GST collected.
- Forgetting to include PAYG withholding amounts on the BAS, resulting in underpayment penalties separate from any GST liability.
- Missing the BAS deadline without contacting the ATO first — the ATO will often waive first-time penalties if you call proactively before the due date.
- Claiming input tax credits on private expenses or purchases without valid tax invoices — the ATO checks this and may disallow credits in an audit.
Frequently Asked Questions
What is the difference between a BAS and an IAS?
A BAS (Business Activity Statement) covers all tax obligations including GST, PAYG withholding, and PAYG instalments. An IAS (Instalment Activity Statement) is a simpler form for businesses that have PAYG withholding or instalments obligations but are not registered for GST. If you become GST-registered, your IAS is replaced by a BAS.
Can I lodge a nil BAS?
Yes. If you had no business activity in a quarter (no sales, no purchases, no wages), you must still lodge a nil BAS by the due date. Failure to lodge is a separate offence from failure to pay, and the ATO can charge penalties even when there is nothing to pay.
What is the GST cash accounting method and who can use it?
Under the cash method, you report GST when payment is actually received or made, rather than when invoices are issued. This is available to businesses with GST turnover under $10 million and helps cash flow by deferring GST obligations until you actually receive payment. You need to apply to the ATO to use this method.
How long does the ATO take to process a BAS refund?
Once you lodge a BAS online, GST refunds are typically processed within 14 business days. Refunds may be delayed if you are a new registrant, the refund is unusually large, or the ATO selects your return for review. Paper lodgements take significantly longer.
Practical Tips
- Reconcile your bank accounts every month rather than waiting until BAS time — a quarterly backlog of transactions is much harder to categorise accurately.
- Use accounting software that connects directly to the ATO via Standard Business Reporting (SBR) to pre-fill and lodge your BAS in one step.
- Set a calendar reminder 2 weeks before each BAS deadline so you have time to chase missing invoices and correct categorisation errors.
- If you have a refund BAS, lodge as early as possible — the ATO processes refunds in the order they are received, and earlier lodgement means earlier cash in your account.
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