Scope & Objective

GST in Australia is a self-assessed, transaction-based tax: a business collects GST on what it sells and claims credits for GST paid on its own purchases, then reports the net position to the ATO on a Business Activity Statement (BAS) — registration, reporting frequency and lodgment deadlines are all separate obligations a business manages itself.

• Businesses approaching or exceeding the $75,000 annual turnover threshold (or $150,000 for non-profit organisations).
• Businesses voluntarily registered for GST below the threshold, deciding between quarterly and annual reporting.
• Finance teams choosing between the three BAS reporting cycles for the first time.
• Businesses that have missed a BAS lodgment deadline and need to understand the penalty exposure.
• Businesses approaching the $20 million turnover threshold that triggers mandatory monthly reporting.

This is a general process guide, not tax advice for a specific business’s accounts. GST thresholds, lodgment dates and penalty amounts referenced below reflect the ATO’s published rules for the 2026–27 financial year; always confirm the current thresholds and dates with an accountant or registered BAS agent before lodging.

Who this guide is for: business owners and finance leads registering for GST for the first time, or reviewing which BAS reporting cycle and lodgment deadlines apply to their business.

Registering for GST

GST registration in Australia is turnover-triggered, not optional once a business crosses the threshold — waiting until the BAS is due to think about registration is already too late.

• Mandatory registration threshold — $75,000 in annual turnover for most businesses, or $150,000 for non-profit organisations.
• The 21-day rule — a business must register for GST within 21 days of its turnover reaching, or being expected to reach, the threshold.
• Voluntary registration — a business below the threshold may still choose to register, which allows it to claim GST credits on purchases but also requires it to charge GST and lodge BAS.
• Registering — is done through the ATO, typically alongside applying for an Australian Business Number (ABN) if the business does not already have one.
• Backdated liability — a business that should have registered earlier can be liable for GST on sales made before it actually registered, even if it never charged customers GST at the time.

Why this matters: registration is what starts the clock on every other GST obligation — the reporting cycle and lodgment deadlines below only apply once a business is actually registered.

Choosing a BAS Reporting Cycle

Once registered, a business reports its GST position on a Business Activity Statement, but not every business reports on the same schedule — the reporting cycle depends mostly on turnover and choice.

• Quarterly reporting — the default cycle for most registered businesses, with four BAS lodgments per year.
• Monthly reporting — compulsory once GST turnover reaches $20 million, and available voluntarily to any business that prefers more frequent reporting.
• Annual reporting — available only to businesses voluntarily registered for GST with turnover under the $75,000 (or $150,000 non-profit) threshold, lodged alongside the business’s income tax return.

A common source of confusion is assuming annual reporting is available to any small business — it is only available to businesses that are voluntarily registered below the turnover threshold, not to businesses that are required to register.

Meeting BAS Lodgment Deadlines

Each reporting cycle carries its own lodgment pattern, and missing which pattern applies to a business is one of the most common causes of an accidentally late BAS.

• Quarterly deadline — the 28th day of the month following the end of the quarter (28 October, 28 February, 28 April, 28 July).
• Agent lodgment concession — registered BAS or tax agents can generally access an extended deadline of about four extra weeks for quarterly BAS, except for the quarter ending 31 December.
• Monthly deadline — the 21st day of the following month, with the December BAS extended to 21 February.
• Annual deadline — 31 October, or 28 February of the following year if the business does not need to lodge an income tax return.
• Lodgment method — generally done online through the ATO’s Business Portal or a registered agent, though paper lodgment remains available in limited cases.

Compliance checklist each period:

• Confirm which reporting cycle currently applies before assuming the previous period’s deadline still applies.
• Reconcile GST collected and GST credits claimed against the underlying sales and purchase records before lodging, not just the accounting software’s default report.
• Lodge on time even if the exact amount payable is still being finalised — an estimate can usually be revised, but a missed deadline cannot be undone.
• Keep records supporting every BAS for at least 5 years.

Late Lodgment Penalties and Interest

Missing a BAS lodgment deadline in Australia triggers penalties that scale with how overdue the statement becomes, plus separate interest on any unpaid amount.

• Failure to Lodge penalty — for small entities, calculated at one penalty unit for every 28 days (or part thereof) the BAS remains outstanding, up to a maximum of five penalty units.
• Medium and large businesses — face proportionally higher penalty unit multiples for the same lodgment failure.
• General Interest Charge (GIC) — accrues daily on any GST amount still unpaid from the day after the payment due date, separately from the lodgment penalty itself.
• Penalty remission — the ATO can, and often will, remit a first-time or genuinely unavoidable late lodgment penalty on request, but this is discretionary and not guaranteed.

Treat the lodgment deadline as fixed regardless of whether the payment amount is fully finalised — lodging an accurate-as-possible BAS on time avoids the lodgment penalty even if a small payment adjustment follows later.

Common GST and BAS Mistakes

• Waiting until turnover clearly exceeds $75,000 before registering, missing the requirement to register within 21 days of reaching or expecting to reach the threshold.
• Assuming annual BAS reporting is available to any small business, when it is only open to voluntary registrants below the turnover threshold.
• Treating the quarterly due date as the same every quarter, missing that agent concessions do not apply uniformly across all four quarters.
• Lodging late because the exact GST payable is still being calculated, instead of lodging an estimate on time and revising it afterward.
• Not requesting remission of a first lodgment penalty, assuming it is automatic when in fact it must be requested.

Most of these mistakes share a root cause: treating GST registration, BAS reporting cycle and lodgment deadlines as one combined task, when in practice each is decided separately and changes on its own trigger — turnover crossing a threshold, a reporting-cycle election, or a fixed calendar date.