According to the ATO, wealthy individuals are resident individuals who, together with their business associates, control net wealth of $5 million or more. The ATO uses sophisticated data matching and analytic models, drawing on tax returns and referrals from other government agencies or the community, to identify wealthy individuals and link them to associated businesses. 

The ATO says it will "engage with" such taxpayers, offering assistance and services to help them "get things right up front". The ATO can tell them what it knows about them, including its view of their group's income tax profile, "so you can work with us where needed".
 

If the information the ATO holds about a wealthy individual is limited, the ATO says it may contact the individual or their tax adviser to better understand their circumstances, and to confirm or correct its view of the individual's wealth and group structure. As part of this engagement, the ATO says the individual will "have the opportunity to check if the information we have about you is correct".

High wealth individuals

Wealthy individuals who control net wealth of $50 million or more are classified as high wealth individuals . Given the importance of this group to community confidence in the tax and super systems, the ATO says it has an ongoing focus on them.

The ATO says if its systems indicate that an individual has effective control of $50 million or more in net wealth, it may ask for validation of the individual's net wealth. The ATO says it will review any information given by high wealth individuals and update its records as required.

Source: www.ato.gov.au/Business/Privately-owned-and-wealthy-groups/What-you-should-know/About-privately-owned-and-wealthy-groups/How-we-identify-wealthy-individuals-and-their-businesses/