Shares in Promina began trading on the Sydney stock exchange after R&SA successfully completed the biggest initial public offering (IPO) in the world so far this year.
Britain's second biggest general insurer said demand for the shares had been strong with shareholders paying 1.80 Australian dollars a share - equivalent to 72p each.
R&SA has been under pressure to plug a £700 million shortfall in its capital reserves required to pay claims and fund new business. The IPO goes some way to filling that gap.
Chief executive Andy Haste said: "The IPO will deliver a major component of the actions we are taking to reshape the group and to strengthen our capital position.
"The capital release from the IPO, together with the release of capital from the sale of our UK healthcare and assistance businesses last month, will significantly improve our risk based capital position. It will also greatly increase our statutory surplus."
Promina owns Australia's third-biggest car and home insurer, New Zealand's biggest combined general and life insurer and the Tyndall fund management business. The company insures more than 2 million cars and almost 1 million homes.
Institutional investors took up 74% of the shares on offer, with retail investors in the UK, US and Asia snapping up the remainder.
The £540 million released from the flotation will be used by R&SA to bolster its battered balance sheet. The insurer has been forced to sell parts of its business after heavy losses from the September 11 terrorist attacks and the impact of flagging world stock markets.
R&SA has also cut 12,000 jobs from its 50,000 strong world workforce, closed its UK life and pensions operation to new business and announced the sale of some divisions. Shares in R&SA rose 1p to 11.55p.