BAS & GST Lodgement Guide for Small Business

What Is a BAS?

A Business Activity Statement (BAS) is a form submitted to the ATO to report your business tax obligations. If your business is registered for GST, you must lodge a BAS — either monthly or quarterly depending on your turnover. Your BAS reports GST collected on sales, GST paid on purchases, PAYG withholding (tax withheld from employee wages), and PAYG instalments (prepaid income tax).

Key BAS Deadlines

• Quarterly lodgement: Due 28 days after the end of each quarter (e.g., Q1 July–Sept is due 28 October)
• Monthly lodgement: Due 21 days after the end of each month
• Annual GST return: For businesses with turnover under $75,000 who report annually — due with your income tax return

Using a registered BAS or tax agent like Optium Accountants may give you additional time to lodge.

How to Prepare Your BAS

1. Reconcile your accounts: Ensure all income and expenses are recorded in your accounting software
2. Check GST codes: Verify that transactions are coded correctly — GST-free, input-taxed, or GST-inclusive
3. Review PAYG withholding: Confirm employee tax withholding amounts match your payroll records
4. Calculate your GST position: GST collected minus GST paid = your net GST obligation
5. Lodge and pay: Submit via your accounting software, the ATO Business Portal, or through your accountant

Common BAS Mistakes

• Incorrectly coding personal expenses as business expenses
• Claiming GST on items that are GST-free (e.g., basic food, some medical services)
• Forgetting to include cash transactions
• Not reconciling bank accounts before lodging
• Missing the lodgement deadline and incurring penalties