Australian BAS and GST: Complete SME Guide
The Business Activity Statement is the single most important filing for Australian SMEs. Here's how to get BAS and GST right.
7 min read · 2 March 2026
GST registration threshold
You must register for GST once turnover reaches or exceeds AUD $75,000 in a 12-month period ($150,000 for non-profits). Ride-share and taxi drivers must register from their first dollar.
Voluntary registration below the threshold lets you claim input tax credits on business purchases — often worth it for B2B service firms.
Business Activity Statement cycle
Registered businesses lodge a BAS monthly (turnover over $20m), quarterly (most SMEs) or annually (small voluntary registrants). BAS reports GST collected, GST paid, PAYG withholding, PAYG instalments and any fringe benefits or fuel tax credits.
Quarterly BAS is due 28 days after the quarter ends (with a further four-week extension if lodged through a tax agent).
Common ATO audit triggers
The ATO's data-matching flags mismatches between BAS and Single Touch Payroll (STP) filings, unusually high GST refunds, and industry benchmarks that fall outside expected ranges.
Keeping tax invoices, contemporaneous logbooks and a reconciled bookkeeping file removes 90% of audit risk.