Finance Minister Mathias Cormann said there were more than $5 billion in retail bids for the private health insurance IPO.

"We about to transfer ownership of Medibank Private to about 400,000 individual shareholders," Mr Cormann said prior to ringing the bell for trade to go live.

"This process has been so successful because of the professionalism of everyone associated with the sale."

The offer raised $5.679 billion for the government and is the second largest IPO on record in Australia. Telstra is the biggest at $US10 billion when it listed in November 1997.

CLSA analyst Jan van der Schalk said the Medibank Private listing was an expensive call on structural, government-led, change.