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Requesting a change to your windfall gains tax assessment

It is your responsibility to tell us if there are any errors on your assessment, and you must contact us within 60 days of the issue date of your assessment or penalties may apply. If you require an amendment to your assessment, please email details to

A failure to notify the Commissioner of an error or omission is a notification default under the Taxation Administration Act 1997. For details on notification default, please refer to Revenue Ruling TAA-008. Penalties may apply for notification defaults. For details on penalty tax and interest, please refer to Revenue Ruling TAA-007v5.

Object to the valuations used in your assessment

Capital improved valuations are used to calculate windfall gains tax.

The capital improved value of a property is the value of the land plus the buildings on it and any other capital improvements.

If you do not agree with the valuations used, you can lodge an objection directly with us.

You must lodge your valuation objection within 2 months of receiving your assessment.

More about valuation objections

Formally object to your assessment

If you believe you have been incorrectly assessed and wish to formally dispute your windfall gains tax assessment, you will need to lodge an objection.

To object to your assessment, you must clearly detail in writing the grounds for your objection.

You can object in writing by post, or by completing our online objection form. Only use one of these methods. You must lodge your objection within 60 days of the issue of the assessment.

Even if you have lodged an objection, you must still pay or defer your windfall gains tax by the due date or you will be charged interest. If your objection is successful, any amount overpaid will be refunded with interest.

Lodge an objection

Last modified: 1 March 2024

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