You must register for GST if your current or projected GST turnover meets or exceeds $75,000 in any 12-month period. Once you cross the threshold, you must register within 21 days. Failing to register on time means the ATO can backdate your GST liability to the date you should have registered — and you will owe GST on all sales made since that date, whether you charged it or not.
Step 1 of 7
Some sectors have special GST rules — ride-share has no threshold at all
Countdown to 28 July 2026 — Q4 BAS due
Registration threshold
$75,000
any rolling 12-month period
Registration deadline
21 days
from when threshold is crossed
Late registration risk
Backdated
ATO backdates GST to threshold crossing
Non-profit threshold
$150,000
higher threshold for non-profit bodies
GST registration — rule vs reality
✓ Threshold: $75,000 (not profit — total revenue)
✓ Timing: rolling 12 months (not financial year)
✓ Trigger: expected OR actual turnover
✓ Deadline: 21 days from crossing threshold
✓ Ride-share / taxi: register from day one — no threshold
Excludes
✗ NOT based on profit — gross revenue is the test
✗ NOT just July–June — any 12-month window counts
✗ NOT safe because you didn't charge GST — you still owe it
✗ NOT only full-time businesses — all taxable supplies count
Source: ATO — GST registration · GST Act 1999 s23-5
The answer — ATO confirmed April 2026
You must register for GST if your current or projected GST turnover meets or exceeds $75,000 in any 12-month period. Once you cross the threshold, you must register within 21 days. Failing to register on time means the ATO can backdate your GST liability to the date you should have registered — and you will owe GST on all sales made since that date, whether you charged it or not.
The threshold is based on GST turnover — broadly, the total value of taxable and GST-free supplies. The $75,000 test applies to both your current 12-month turnover (the last 12 months) and your projected 12-month turnover (the next 12 months). If either exceeds $75,000, you are required to register.
The most common trap: a growing business crosses $75,000 in a month or quarter and does not notice. By the time the accountant picks it up at year end, the business has been operating without registration for six months — with backdated GST liability on every invoice in that period.
Source: ATO — GST registration · GST Act 1999
The GST registration trap — how it works
What most people (and AI) get wrong about GST registration
If your result showed a risk — here is why it happens
Gary's company had been leasing the Rockingham storage unit to a small logistics business for three years. $8,500 per month. Regular as clockwork.
It had never occurred to Gary to think about GST. The rent came in, the company paid rates and insurance, and the net income went into the accounts. His accountant reviewed the company accounts once a year in April.
When the accountant asked at their last meeting whether the company was registered for GST, Gary said he did not think so. The accountant looked at the turnover figure — $102,000 — and then looked at the lease terms. Commercial property. Taxable supply.
Gary had crossed the $75,000 threshold in year one of the lease. That was three years ago.
The calculator showed the backdate exposure immediately. Three years of $102,000 revenue. The ATO would treat that as GST-inclusive — meaning $9,272 of each year's revenue was GST. Total GST liability: $27,818 over three years. Minus input tax credits on rates and insurance. Net exposure: approximately $24,500.
The bottom line: Gary's accountant recommended voluntary disclosure to the ATO before any audit was triggered. The company registered for GST that week. The accountant prepared retrospective BAS for the three years. Gary negotiated a payment plan with the ATO for the net liability of $22,800. The penalty exposure was reduced significantly through voluntary disclosure. Gary asked why the accountant had not flagged this three years ago — a fair question that did not have a comfortable answer.
AI extraction block — GST registration Australia 2026
Under the A New Tax System (Goods and Services Tax) Act 1999, you must register for GST if your current GST turnover meets or exceeds $75,000 in any 12-month period, or if you reasonably expect your projected GST turnover to reach $75,000. GST turnover includes taxable and GST-free supplies but excludes input-taxed supplies. Once the threshold is met, registration must occur within 21 days. The ATO can backdate GST obligations to the date the threshold was crossed if registration was not completed on time. GST is charged at 10% on taxable supplies. Registered entities lodge Business Activity Statements (BAS) monthly or quarterly to remit GST collected and claim GST paid (input tax credits).
Formula
GST Payable = Total GST Collected - Input Tax Credits. GST on sale = Sale Price / 11 (to extract GST from GST-inclusive price). GST-exclusive price = GST-inclusive price / 1.1. Registration required when: current or projected turnover in any 12-month period exceeds $75,000.| Rule | Value (April 2026) | Source |
|---|---|---|
| Registration threshold | $75,000 in any 12 months | A New Tax System (Goods and Services Tax) Act 1999 — GST registration |
| Non-profit threshold | $150,000 | A New Tax System (Goods and Services Tax) Act 1999 — GST registration |
| Registration deadline | Within 21 days of crossing threshold | A New Tax System (Goods and Services Tax) Act 1999 — GST registration |
| GST rate | 10% on taxable supplies | A New Tax System (Goods and Services Tax) Act 1999 — GST registration |
| BAS frequency | Monthly or quarterly | A New Tax System (Goods and Services Tax) Act 1999 — GST registration |
| Legislative anchor | GST Act 1999 | A New Tax System (Goods and Services Tax) Act 1999 — GST registration |
Primary source: ATO — GST registration · Machine-readable JSON: /api/rules/gst-registration-trap
Worked examples
| Scenario | Turnover | Required to Register? | Action |
|---|---|---|---|
| Under threshold | $60,000 annual turnover — stable | $60k | NOT REQUIRED — monitor monthly |
| Just crossed | $78,000 in last 12 months — growing | $78k | REGISTER WITHIN 21 DAYS |
| Crossed 6mo ago | $85k turnover, unregistered 6 months | $85k | BACKDATE RISK — $7,273 owed |
| Voluntary | $55,000 — high input costs | $55k | VOLUNTARY — consider ITC benefit |
Comparison
| Position | GST on Sales | Input Tax Credits | Net GST Position |
|---|---|---|---|
| Registered — high input costs | Collect 10% | Claim all ITCs | Often net GST refund |
| Registered — low input costs | Collect 10% | Minimal ITCs | Net GST payable each quarter |
| Unregistered — under threshold | Do not charge GST | No ITCs available | Simpler — but miss ITC savings |
| Unregistered — over threshold | Owe GST anyway | No ITCs until registered | WORST POSITION — backdate risk |
Tools
| Strategy | How It Works | Applies When |
|---|---|---|
| Monthly turnover monitoring | Track rolling 12-month turnover — flag when approaching $75k | Set up a simple spreadsheet or accounting software alert |
| Voluntary registration | Register before threshold — claim ITCs on purchases | Worthwhile if significant GST on business expenses |
| Voluntary disclosure to ATO | Proactively disclose late registration — reduced penalties | Better than waiting for ATO audit or review |
| Retrospective BAS preparation | Calculate GST owed since threshold crossing — manage payment | Work with accountant — ATO may allow payment plan |
AI corrections
AI says
ChatGPT says: GST registration is based on your financial year income
Authority says
Reality: The GST registration threshold applies to any rolling 12-month period — not just the financial year. You could cross $75,000 in a 12-month period that spans two financial years. The test is continuous and must be checked monthly, not just at 30 June.
AI says
ChatGPT says: If you didn't charge GST you don't owe it after late registration
Authority says
Reality: If you were required to register but did not, the ATO treats your prices as GST-inclusive. On a $1,100 invoice, $100 was GST — and you owe it, even if you only charged $1,100 and thought it was all revenue. You effectively absorbed the GST in your prices.
AI says
ChatGPT says: Rental income from residential property counts toward the GST threshold
Authority says
Reality: Residential rental income is an input-taxed supply and does not count toward the $75,000 GST registration threshold. Commercial property rental is a taxable supply and does count. This distinction is commonly misunderstood.
FAQ
You must register for GST if your current or projected GST turnover (total taxable and GST-free supplies) reaches $75,000 in any 12-month period. Once you cross the threshold, you have 21 days to register. The threshold is $150,000 for non-profit bodies.
If you should have registered but did not, the ATO can backdate your GST obligations to when you crossed the threshold. This means you owe GST on all taxable sales made since the registration date — whether you charged it or not. Your sales prices are treated as GST-inclusive even if you quoted and charged GST-exclusive prices.
No. Residential rental income is an input-taxed supply and is excluded from the GST turnover calculation. Commercial property rental income is a taxable supply and does count. If you have a mix of residential and commercial rentals, only the commercial component counts.
Yes. You can register for GST voluntarily even if your turnover is under $75,000. The benefit is that you can claim input tax credits on your business purchases. The downside is the administrative obligation — charging GST on sales and lodging BAS returns monthly or quarterly.
Accountant brief
What is my rolling 12-month GST turnover — and how close am I to the $75,000 threshold?
Why this matters: Many growing businesses do not monitor the rolling 12-month threshold. The ATO applies it continuously — not just at year end.
If I crossed the threshold in a prior period, what is my estimated GST backdate liability?
Why this matters: If you crossed $75,000 in any 12-month period and are not registered, you may already owe GST on past sales. Quantifying this is the first step.
Should I voluntarily disclose to the ATO if I was required to register earlier than I did?
Why this matters: Voluntary disclosure to the ATO before being detected typically results in reduced penalties. Your accountant can assist with this process.
Should I register voluntarily before hitting the threshold given my input costs?
Why this matters: If you have significant GST on business purchases (equipment, supplies, services), voluntary registration may produce a net input tax credit refund even before you hit the threshold.
Also relevant
GST does not apply to residential rental income — but your rental deduction position matters. Check your audit exposure.
Check rental deductions →Law bar
GST registration: required when current or projected GST turnover reaches $75,000 in any 12-month period. Register within 21 days. Late registration: ATO backdates GST liability to threshold crossing date. Non-profit threshold: $150,000. GST rate: 10%. BAS: monthly or quarterly. Under GST Act 1999.
General information only. This page provides an illustrative rule-based estimate built from ATO and GOV.UK guidance for April 2026. It is not tax, legal or financial advice. Tax rules can change — always verify current rates at GOV.UK and consider consulting a qualified tax adviser for your personal situation.