But taxpayers in Wollongong's poorer suburbs are doing better than several areas in NSW, with average incomes exceeding some parts of Sydney and remote areas in the state's west.

New statistics released by the Australian Tax Office (ATO) show the nation's wealthiest postcode was 6011 - Peppermint Grove and Cottersloe in Western Australia - had a massive leap in income to an average of more than $300,000.

This was a jump of more than 80 per cent between the 2018-19 and 2019-20 financial years, as the nation slumped into recession for the first time in almost three decades.

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Residents of postcode 2502 - Wollongong's southern suburbs of Warrawong, Primbee, Lake Heights and Cringila - have the lowest average income in the Illawarra at $49,554, according to the latest ATO income data available, from 2019-20.

With an average taxable income of $80,566, the northern postcode of 2515 - from Thirroul to Clifton - is the Illawarra's wealthiest. It is followed by Bulli (2516) with an average income of $75,660, then 2508 (Helensburgh and Stanwell Park) on $71,984.

Postcode 2500 (Wollongong city) had an average taxable income of $59,707 while Port Kembla, postcode 2505, had an average taxable income of $56,898.

Shellharbour's 2529 postcode, from Oak Flats to Shell Cove, had an average income of $61,696 while 2530 (Dapto) was at $57,674.

The stats showed income growth was significantly slower in the less wealthy suburbs. From 2019 to 2020, the average income for postcode 2515 rose by $1810 - 2.3 per cent. Not a great amount - compared with postcode 6011 - but significantly higher growth than the Illawarra's less affluent postcodes.

In Port Kembla, the average income rose by $883 (1.6 per cent), and in postcode 2052, Lake Heights to Primbee, by just $281 - about 0.6 per cent.

It is likely these less wealthy suburbs will show slower growth when more recent figures illustrate the effect of the pandemic on less secure work.

The stats showed that while Wollongong's poorer

In Berkeley, postcode 2506, the average taxable income actually dropped between the 2019 and 2020 financial years - from $52,826 to $52,443. And in 2530, Dapto, income dropped $73 to an average $57,674.

The information is based on individuals' income tax returns, of which the ATO processed about 15 million.

Some of the state's least wealthy areas - in Auburn and Fairfield - were in Sydney, as were eight of the nation's top ten earning postcodes, clustered around the harbour and north shore. Western NSW also had several of the least affluent areas.