What Is a BAS and When Do Sole Traders Need to Lodge One?

By Dan Reeve — Working handyman and founder of SMASH Invoices. Built SMASH after losing $1,200 in uninvoiced jobs in a single year. He still takes on handyman work and uses SMASH on every job. About Dan →

A BAS (Business Activity Statement) is a quarterly tax report submitted to the ATO that reconciles the GST you collected on sales against the GST you paid on purchases. GST-registered sole traders must lodge a BAS for each quarter, for the periods ending September 30, December 31, March 31, and June 30. Each BAS is due approximately one month after the quarter ends. If you are not GST-registered, you do not need to lodge a BAS.

What a BAS actually reports

Your BAS has three core numbers:

G1: Total sales All taxable sales you made in the quarter, the total including GST.

1A: GST collected on sales The GST component of all sales. If you issued $10,000 in invoices, the GST portion is $909 (GST = total ÷ 11).

1B: GST paid on purchases The GST you paid on business purchases, tools, materials, vehicle expenses, insurance, subscriptions. Keep receipts. Every one of these reduces what you owe.

Net GST: 1A minus 1B This is what you pay or receive. If you collected $909 in GST and paid $400 in GST on purchases, your net payment to the ATO is $509.

BAS due dates for Australian sole traders

Registered tax agents get extended deadlines on behalf of their clients, another reason many sole traders use a BAS agent.

How invoicing properly makes BAS simple

Your BAS is only as accurate as your invoices. If you have gaps, jobs done without invoices, materials bought without keeping receipts, your BAS figures will be wrong.

Good invoicing practice makes BAS a 2-hour task:

1. Export all invoices for the quarter from your invoicing app
2. Add up all taxable sales → G1
3. Divide by 11 → that's your GST collected (1A)
4. Add up all GST-inclusive receipts from business purchases
5. Divide by 11 → that's your GST credits (1B)
6. 1A minus 1B = net payment

SMASH Invoices stores all invoices by date with totals. The Pro and Unlimited plans include CSV export, hand the file to your BAS agent or use it directly for your BAS calculation.

Frequently asked questions

Does every sole trader have to lodge a BAS? No. Only sole traders registered for GST are required to lodge a BAS. If you're not GST-registered (turnover below $75,000 and no voluntary registration), you do not lodge a BAS.

Can I lodge my BAS myself? Yes. You can lodge via the ATO's Business Portal, through accounting software like Xero or MYOB, or through a registered BAS agent. Most sole traders with straightforward finances lodge their own BAS. BAS agents typically charge $100–$200 per quarter.

What happens if I miss a BAS deadline? Late lodgement results in a Failure to Lodge penalty, typically $222 for each 28-day period the BAS is overdue. Late payment of the GST liability results in interest charges on the outstanding amount. Contact the ATO proactively if you can't lodge on time, they often waive first-time penalties with a phone call.

What records do I need for my BAS? You need all invoices you issued (your sales), all receipts for business purchases (your input tax credits), and your ABN. The ATO requires records to be kept for 5 years. Digital records, invoice exports, receipt photos, bank statements, are accepted.

How does correct invoicing make BAS easier? Every missing invoice is missing income. Every missing receipt is a missed input tax credit. Tradies who invoice consistently and keep receipts systematically spend 2–3 hours per quarter on BAS. Those who reconstruct from memory spend 2–3 days, and get it wrong more often.

Invoice at the job. BAS at the end of quarter. Both done right. Start Free →

Internal links: The EOFY invoicing checklist · Do I need to register for GST as a sole trader?