The Ultimate BAS Guide for Small Businesses in 2026

The Business Activity Statement (BAS) is often the sharpest thorn in the side of a small business owner. But missing a lodgement deadline or claiming incorrect GST credits can trigger costly ATO audits. Here is exactly what you need to know.

What Exactly is a BAS?

If your business has an ABN and is registered for GST (mandatory if your gross income exceeds $75,000), you must lodge a BAS. The ATO uses this statement to collect various taxes, including Goods and Services Tax (GST), Pay As You Go (PAYG) instalments, PAYG withholding tax, and other taxes.

Common BAS Mistakes Costing You Money

We review countless files from new clients coming to us in Melbourne's western suburbs. Time and time again, we see the same errors:

• Claiming GST on GST-Free items: Bank fees, basic foods, and water rates do not have GST. Claiming them is an immediate red flag.
• Missing out on viable claims: Not having a system to capture smaller receipts, meaning you miss out on legitimate business expense credits.
• Incorrect Motor Vehicle Claims: Only the business use portion of vehicle expenses can be claimed. Are you maintaining a logbook?

Deadlines You Cannot Miss

For quarterly lodgements, the standard due dates are:

• Q1 (Jul-Sep): 28 October
• Q2 (Oct-Dec): 28 February
• Q3 (Jan-Mar): 28 April
• Q4 (Apr-Jun): 28 July

Pro Tip: Clients lodging through a registered BAS Agent, or a service supervised by one (like Numenity), can receive an automatic four-week extension on lodgement and payment dates for most quarters!

Stop Stressing Over ATO Compliance

At Numenity, our bookkeeping services are performed under the supervision of a registered BAS Agent, locally in Melbourne. We implement flawless Xero setups that pull in your bank feeds automatically, meaning your BAS practically writes itself by the end of the quarter.