How to Do Your Own BAS as a Sole Trader

If you run a sole trader business in Australia and you are registered for GST, you need to lodge a Business Activity Statement (BAS) with the ATO. Most sole traders pay an accountant $150 to $350 per quarter to do this. Some pay more.

But here is the thing: BAS is not complicated. If you have clean bank records, you can do it yourself. This guide shows you how, step by step.

Do you actually need to lodge a BAS?

You need to lodge a BAS if:

• Your business is registered for GST (compulsory once your turnover hits $75,000, optional before that)
• You have PAYG withholding obligations (you pay employees or contractors who did not quote an ABN)
• You are making PAYG instalment payments (the ATO has told you to pay income tax in instalments)

If you are under $75,000 turnover and not registered for GST, you do not need to lodge a BAS. Simple as that.

What goes on your BAS

For most sole traders, the BAS boils down to three things:

1. GST collected - the GST component of everything you sold (10% of your GST-inclusive income). This is label 1A.
2. GST paid - the GST component of your business purchases. This is label 1B.
3. PAYG instalments - if the ATO has sent you a PAYG instalment amount or rate, you report it here.

The ATO's BAS form has more labels (G1 through G20), but most sole traders only need G1, G2, G3, G10, G11, 1A, 1B, and Item 5 (net GST). If you are using the simpler BAS option (available to businesses with turnover under $10 million), it is even shorter.

Log into your bank and download your transactions as a CSV file for the BAS quarter. All major Australian banks support this:

• CBA: NetBank > Transactions > Export > CSV
• NAB: Internet Banking > Transaction History > Download > CSV
• ANZ: Internet Banking > Account > Export Transactions > CSV
• Westpac: Online Banking > Transactions > Export > CSV

Make sure you select the correct date range for the quarter:

Quarter	Period	Due date
Q1	1 Jul - 30 Sep	28 Oct
Q2	1 Oct - 31 Dec	28 Feb
Q3	1 Jan - 31 Mar	28 Apr
Q4	1 Apr - 30 Jun	28 Jul (if lodging electronically) or 28 Aug

This is where most of the work is. Each transaction needs three things:

1. Income or expense? Money coming in or going out.
2. Category - what type of income or expense (sales, materials, fuel, phone, rent, etc.)
3. GST status - does this transaction include GST?

The GST status is the tricky part. Here is a quick reference:

Transaction type	GST status	Why
Bunnings, Officeworks, tools	GST included	Standard retail purchase
Fuel	GST included	Fuel has GST (you may also claim fuel tax credits)
Insurance premiums	GST included	Most business insurance includes GST
Bank fees, interest	GST-free	Financial supplies are input-taxed
Wages, super	GST-free	Not a taxable supply
Government fees, fines	GST-free	Not subject to GST
Rent (commercial)	GST included	If landlord is GST-registered
Rent (residential)	Input-taxed	Residential rent is input-taxed
Personal expenses	N/A	Exclude from BAS entirely

The hard way: Go through your bank CSV line by line in Excel. For 200+ transactions per quarter, this takes 2 to 4 hours.

The fast way: Use a tool like TaxBench to upload the CSV and have AI categorise every transaction automatically. Review and correct any mistakes, then export your BAS numbers. Takes about 10 minutes.

Once every transaction is categorised, add up:

• G1: Total sales (including GST)
• G2: GST-free sales (exports, medical, food staples)
• G3: GST-free sales that are input-taxed (financial, residential rent)
• 1A: GST on sales = (G1 - G2 - G3) / 11
• G10: Capital purchases (equipment over $300, vehicles)
• G11: Non-capital purchases (materials, fuel, rent, phone)
• 1B: GST on purchases = (G10 + G11) / 11
• Item 5: Net GST = 1A minus 1B (positive means you owe the ATO, negative means refund)

If you use TaxBench, these numbers are calculated automatically from your categorised transactions.

Go to bp.ato.gov.au (ATO Business Portal) or through myGov. Select your BAS for the quarter and enter the numbers from step 3. Review, submit, done.

If you owe GST (Item 5 is positive), you can pay via BPAY, credit card, or direct debit. The payment reference number is on the portal.

Common mistakes to avoid

• Claiming GST on GST-free items. Bank fees, insurance stamp duty, government charges, and wages do not have GST. Claiming them inflates your 1B and reduces your payment (or gets you a refund you should not get). The ATO audits this.
• Including personal expenses. If you use one bank account for business and personal, you need to exclude personal spending from BAS. TaxBench flags personal-looking transactions so you can exclude them.
• Wrong quarter dates. Make sure your bank CSV covers exactly the right dates. One week of overlap or gap throws everything off.
• Forgetting to lodge. Late BAS attracts a penalty of $313 per 28-day period, up to $1,565. Set a reminder for 2 weeks before the due date.
• Not keeping records. You must keep BAS records for 5 years. Keep your bank CSVs and the final BAS summary.

How much you will save doing it yourself

Method	Cost per quarter	Annual cost	Time per quarter
Accountant	$150 - $350	$600 - $1,400	0 (but 1-2 weeks turnaround)
Full accounting software (Xero/MYOB)	$25 - $65/mo = $75 - $195	$300 - $780	30 min (ongoing maintenance)
TaxBench (CSV upload)	$29	$116	10 - 15 min
Manual (spreadsheet)	$0	$0	2 - 4 hours

The bottom line

BAS is not hard. It is tedious. The actual work is categorising transactions and adding up GST. If you are willing to spend 10 minutes reviewing AI-categorised transactions instead of 3 hours in a spreadsheet, you can do your own BAS and keep the $300+ per quarter your accountant charges.

Your accountant is still valuable for complex stuff (trusts, capital gains, tax planning). But for straightforward quarterly BAS? You can handle it.