What Happens If You Register for GST Late: Penalties, Backdating & How to Fix It

Understanding the GST Registration Threshold and Obligation

Under Australian tax law, you must register for Goods and Services Tax (GST) if your GST turnover meets or exceeds the registration threshold. For most businesses, the threshold is $75,000 per annum (or $150,000 for non-profit organisations). The obligation arises from the moment you have a reasonable expectation of exceeding the threshold, not just when you actually do.

GST turnover includes all supplies made in the course of your enterprise, excluding input-taxed supplies and supplies that are not connected with Australia. If you are a sole trader or small business operator, you must monitor your turnover monthly. Importers face a different rule: you must register for GST if you import goods into Australia, regardless of turnover, unless an exemption applies (e.g., low-value imports under $1,000).

Expert Tip: The ATO considers your projected turnover, not just historical figures. If you start a new business and expect to exceed $75,000 in the first year, you must register from day one. Failure to do so can trigger penalties from the first month of operation.

Immediate Consequences of Late GST Registration

When you register for GST after the required date, several immediate consequences take effect. The most critical is that you become liable for GST on all taxable supplies made from the date you should have registered. This means you must account for GST on sales you made while unregistered, even if you did not charge GST to your customers.

Additionally, you lose the ability to claim input tax credits for purchases made before your registration date, subject to the 28-day rule (see below). The ATO will also impose penalties and interest charges. For many small businesses, the financial impact can be severe, especially if they have been operating for months or years without registration.

• Backdated GST liability: You must pay GST on all taxable supplies from the date you were required to register.
• Loss of input tax credits: You cannot claim credits for purchases made before registration, except in limited circumstances.
• Penalties and interest: The ATO will issue a failure-to-register penalty and charge general interest on any unpaid GST.
• Reputational risk: Late registration may trigger an ATO audit or review of your entire tax history.

Penalties and Interest Charges from the ATO

The ATO imposes two main types of financial penalties for late GST registration: a failure-to-register penalty and a general interest charge (GIC). The failure-to-register penalty is calculated as a flat amount per 28-day period that you were unregistered, up to a maximum of 75 penalty units. As of the 2024–25 financial year, one penalty unit is $313, so the maximum penalty is $23,475. However, the ATO often applies a reduced penalty for first-time offenders or if you voluntarily disclose the error.

The general interest charge applies to any GST you should have paid but did not. The GIC rate is set quarterly and is currently around 11% per annum (check the ATO website for the latest rate). Interest accrues from the original due date of each BAS period until the date you pay the outstanding amount.

Warning: The ATO can also issue a penalty for failing to lodge BAS on time if you were required to lodge while unregistered. This is a separate penalty of up to $1,565 per 28-day period.

Loss of Input Tax Credits: The 28-Day Rule

One of the most misunderstood consequences of late GST registration is the loss of input tax credits (ITCs). Under the 28-day rule, you can only claim ITCs for purchases made before your registration date if you register within 28 days of becoming required to register. If you register later than 28 days, you lose the right to claim ITCs for any purchases made before the registration date.

For example, if you exceeded the $75,000 threshold on 1 March and register on 15 April (45 days later), you cannot claim ITCs for purchases made between 1 March and 15 April. However, you can claim ITCs for purchases made on or after the registration date. This rule applies even if you backdate your registration (see next section).

There is a limited exception: if you can demonstrate that you had a reasonable excuse for the delay and that the ATO exercises its discretion, you may be able to claim some ITCs. But this is rare and requires a formal application.

Backdating Your GST Registration: When and How

If you register for GST late, the ATO will generally backdate your registration to the date you were required to register. This is automatic for mandatory registrations. For voluntary registrations, you can request backdating up to 4 years from the date of application, provided you meet certain conditions (e.g., you were carrying on an enterprise and had an ABN).

Backdating means your GST registration is treated as if it existed from the earlier date. However, backdating does not automatically restore your right to claim ITCs for pre-registration purchases. The 28-day rule still applies. Also, backdating may increase your GST liability because you must account for GST on all supplies made during the backdated period.

1. Step 1: Log in to the ATO Business Portal or use a registered tax agent to apply for GST registration.
2. Step 2: Indicate the date you want the registration to start. For mandatory registration, the ATO will set the start date to the date you exceeded the threshold.
3. Step 3: Lodge all outstanding BAS for the backdated period. You will need to calculate GST on sales and claim any eligible ITCs (subject to the 28-day rule).
4. Step 4: Pay any GST owed plus penalties and interest. The ATO may offer a payment plan if you cannot pay in full.

Impact on Pricing and Invoicing

Late registration creates a pricing dilemma. If you did not charge GST to your customers during the unregistered period, you cannot go back and add GST to past invoices. You must absorb the GST liability from your own pocket. This can significantly reduce your profit margins, especially if you operated for a long time without registration.

For future invoices, you must immediately start charging GST at 10% and issue tax invoices. You also need to update your pricing, website, and contracts to reflect that you are now GST-registered. If you have long-term contracts with customers, you may need to renegotiate prices to include GST, as the ATO expects you to pass on the GST to customers.

For importers, late registration can affect customs clearance. If you import goods without a valid GST registration, the Australian Border Force may require you to pay GST at the border, and you may not be able to claim a refund or credit until you register.

Special Considerations for Importers

Importers face unique risks with late GST registration. Under the GST on importation rules, you must pay GST on most imported goods at the time of entry. If you are not registered for GST, you cannot claim an input tax credit for that GST. This means the GST becomes a real cost to your business.

If you register late, you may have imported goods while unregistered and paid GST at the border. You can claim a refund of that GST only if you register and then apply for a refund through your BAS. However, the refund is limited to the GST paid on goods imported within the 4-year amendment period. Additionally, if you were required to register earlier, the ATO may treat the GST paid at the border as a credit against your GST liability, but you must still account for GST on the sale of those goods.

• Action: If you import goods regularly, register for GST before your first import to avoid double costs.
• Action: Keep records of all import declarations and GST paid at the border to support future ITC claims.
• Action: Consider using a customs broker who can advise on GST registration requirements.

Steps to Rectify Late Registration

If you discover that you should have registered for GST earlier, take immediate action to minimise penalties and interest. The ATO encourages voluntary disclosure, which can reduce penalties by up to 80% in some cases.

1. Assess your situation: Determine the date you were required to register. Review your turnover records and any import activity.
2. Register for GST: Apply online via the ATO Business Portal or through your tax agent. Indicate the correct start date.
3. Lodge outstanding BAS: Prepare and lodge BAS for each period from the required registration date to the present. Calculate GST on sales and claim eligible ITCs.
4. Pay any amount owing: Pay the GST, penalties, and interest. If you cannot pay, contact the ATO to set up a payment plan.
5. Seek professional advice: Engage a registered tax agent or BAS agent to help with calculations and negotiations with the ATO.

Expert Tip: The ATO’s Voluntary Disclosure policy can significantly reduce penalties. Disclose before the ATO contacts you for maximum benefit. Use the ATO’s online form or speak to your tax agent.

GST Calculator & Tools

To help you manage your GST obligations, gstcalculatorau.com offers a full suite of free calculators. Use our GST Calculator to quickly determine the GST component of any transaction, or our GST Registration Date Calculator to estimate when you should have registered based on your turnover history.

Step-by-step guide to using the GST Calculator:

1. Visit gstcalculatorau.com and select the “GST Calculator” tool.
2. Enter the total amount (including or excluding GST) and choose the calculation direction.
3. Click “Calculate” to see the GST amount and the base price.
4. For backdating scenarios, use the “Turnover Tracker” to input monthly sales and identify the month you exceeded the threshold.

Our Searchable GST Database lets you look up how GST applies to specific goods, services, and transactions. This is especially useful for importers and small businesses dealing with complex supplies.

Common GST Mistakes to Avoid

• Ignoring the threshold: Many sole traders assume they are below $75,000 but forget to include all income streams (e.g., side hustles, online sales).
• Delaying registration after exceeding threshold: The 28-day rule for ITCs is strict. Register as soon as you know you will exceed the threshold.
• Not backdating correctly: When registering late, ensure the start date matches the date you were required to register. Incorrect dates can lead to further penalties.
• Failing to lodge BAS for backdated periods: Even if you register late, you must lodge BAS for all periods from the required date. Missing lodgements attracts additional penalties.
• Claiming ITCs for pre-registration purchases after 28 days: Unless you have a reasonable excuse, do not claim these credits. The ATO will disallow them and may impose penalties.
• Not updating invoices and pricing: After registration, all invoices must show your ABN and GST amount. Failure to issue tax invoices can result in penalties.

Conclusion

Late GST registration in Australia carries significant financial and administrative consequences, including backdated GST liability, loss of input tax credits, and ATO penalties. However, by understanding the rules and acting promptly, you can minimise the damage. The key takeaways are: monitor your turnover regularly, register as soon as you exceed the threshold, and use voluntary disclosure to reduce penalties. For importers, register before your first import to avoid double costs.

Use the tools and database at gstcalculatorau.com to stay compliant and make informed decisions. If you are unsure about your situation, consult a registered tax agent or BAS agent for personalised advice.