Question 15
At Question 15 of the supplementary return, you must disclose whether, during the period the return covers:
- you have identified any material GST reporting errors (impacting periods within the 4-year period of review)
- you have claimed material amounts of input tax credits in a business activity statement (BAS) referable to earlier periods.
If you select 'Yes', you must provide for:
- material GST reporting errors, a description of the error, the amount, how it has been rectified and addressed going forward
- input tax credits referable to earlier periods, the amount, a description of what gave rise to the entitlement and any methodology used to determine the amount.
What is a GST reporting error?
A GST reporting error is a mistake you made in working out your GST net amount on your business activity statement (BAS) impacting periods within the 4-year period of review that would, if it was the only mistake that you made, result in you:
- reporting or paying too much GST (credit error)
- reporting or paying too little GST (debit error).
The GST reporting error is material where the gross amount of the error exceeds your entity's materiality threshold in GST.
Your materiality threshold is:
- $500,000 for Top 100 taxpayers
- $250,000 for Top 1,000 taxpayers.
Note that you can only correct GST reporting errors in a later BAS in line with the approach and limits specified in LI 2023/32 A New Tax System (Goods and Services Tax) (Correcting GST Errors) Determination 2023.
Whether you corrected the error by revising an earlier BAS or in a current BAS, you should disclose any material errors identified in the period in your return.
When do credits claimed in a later BAS need to be disclosed?
You also need to disclose material amounts of input tax credits referable to earlier periods, where both of the following apply:
- The credits are claimed in a BAS in the period the return covers, where the credits were originally attributable to periods prior to that period.
- The credits arise due to a change in the GST treatment of your supplies or acquisitions. This includes changes to the extent of creditable purpose of acquisitions under Division 11 or Division 70 of the GST Act.
Amounts will be material where the input tax credits claimed in the period the return covers exceeds your entity's materiality threshold.
Your materiality threshold is:
- $500,000 for Top 100 taxpayers
- $250,000 for Top 1,000 taxpayers.
Resources to help you answer this question
In answering this question, you should consider the materiality of any GST errors you have identified during the period the return covers:
- You should disclose material GST errors identified in the period that the return covers, regardless of which periods within the 4-year period of review the error impacts.
- Errors identified in the period that the return covers should be disclosed whether they have been corrected or not. However, you should not wait to lodge your Supplementary annual GST return to correct an error.
For more information on correcting GST errors, see Correcting GST errors or LI 2023/32.
You should also disclose material amounts of input tax credits you have claimed in the period the return covers which were originally attributable to earlier periods outside the financial year.
You only need to disclose input tax credits arising due to a change in the GST treatment of your supplies or acquisitions. For example:
- You should disclose instances that are material where you retrospectively change your input tax credit claim under Division 11 (such as, applying a different apportionment method or rate to determine intended use) or Division 70 (such as, where you identify that an acquisition does qualify for reduced input tax credits).
- You do not need to disclose input tax credit amounts attributable to June 2025 that were processed and claimed in your July 2025 BAS due to a processing delay, where there is no change in GST treatment.
- You do not need to disclose Division 129 adjustments as these are not GST reporting errors or additional input tax credits referable to earlier periods.
Example 1: 'Yes' at Question 15
Lanyon Industries is a Top 1,000 taxpayer who has a combined assurance review completed in 2023. Lanyon Industries supplies a mix of GST-free and taxable food and health products.
In line with its governance processes, in August 2025 Lanyon Industries undertakes a periodic self-review of the GST classification of its products. It identifies a product that was incorrectly classified as GST-free, instead of taxable. This error results in a shortfall of $300,000 over the tax periods since it started selling the product in late 2024. Lanyon Industries submits a voluntary disclosure of the amounts in September 2025.
In completing the supplementary return, Lanyon Industries answers 'Yes' at Question 15 and discloses that it has an error of $300,000 due to the incorrect GST classification of prepared meals. Lanyon Industries explains that it has rectified the error by making a voluntary disclosure (including the date of the correspondence) and by updating the relevant system with the correct GST codes going forward.
Lanyon Industries retains evidence to support its response at Question 15.
End of example
Example 2: 'Yes' at Question 15
Callaway Finance is a Top 100 taxpayer. As part of its periodic GST controls testing plan, Callaway Finance tests the operating effectiveness of its procedures to apply the reverse charge to acquisitions from offshore.
In April 2026, this testing identifies that certain subsystems were inadvertently not set up with built-in controls to apply the reverse charge. This resulted in an additional GST liability of $1,250,000 within the 4-year period of review.
When completing the supplementary return, Callaway Finance answers 'Yes' at Question 15, and discloses the error, stating it has made a voluntary disclosure of the shortfall (giving the date of the correspondence) and briefly advising how it has updated its systems and processes going forward.
In June 2026, while monitoring and reviewing its reduced input tax credit claims, Callaway Finance identify a separate issue where it is entitled to additional credits of $260,000 in relation to reduced input tax credits on brokerage services. These refer to earlier periods outside the 2025–26 financial year.
It does not include this at Question 15, as it is under the materiality threshold for a Top 100 taxpayer.
However, Callaway Finance discloses both issues in real-time to our engagement team in line with our disclosure expectations for Top 100 taxpayers in the Top 100 pre-lodgment disclosures framework.
Callaway Finance retains evidence to support its response at Question 15.
End of exampleContinue to Section G: Declaration and signature.
Return to Supplementary annual GST return 2026 instructions.