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The ATO amnesty for funds hidden in offshore accounts comes with a warning for those that don't take it up. Photo: Michael O'Sullivan

The Tax Office is allowing Australians with money parked in offshore accounts to avoid harsh penalties by coming forward, in an amnesty program worth up to half a billion dollars.

ATO Commissioner Chris Jordan will announce the program today, which will reduce the penalties for taxpayers who hand over information about their hidden accounts over the past four years.

The program is being drummed up as the 'last chance' for tax evaders to make peace with the Tax Office, before greater information sharing powers with overseas jurisdictions come into effect.

''We're getting into a world where there may be a lot more automatic exchange of information,'' ATO Deputy Commissioner Michael Cranston said.

''What we're saying to taxpayers who have stayed hidden is, one day you will get caught. And it will be a lot worse for you when you do.''

The program is targeting rich individuals but Mr Cranston said there was nothing to stop a company such as Google or Apple from coming forward.

''If they've concealed some income from the Australian tax authorities and want to disclose it to us, we would have a look at it,'' he said.

Efforts by the government to claw back revenue from tax havens were stalled recently, with Treasury admitting its new treaty with Switzerland doesn't go far enough to catch evaders who have already pulled their money out of their accounts.

But the tax office said the global push towards greater transparency was closing loopholes and prompting new agreements with previously secretive nations.

"We have very effective exchange arrangements with those countries where people might have parked their assets and incomes, such as (British Virgin Islands), Bermuda, Gernsey, Jersey and even Switzerland," Mr Cranston said.

"If you think your Swiss bank account is going to be protected going forward, well, that is not going to happen."

The ATO said the amnesty program would bring in up to $500 million in otherwise lost revenue for the government, as well as bringing assets back into the Australian tax system for future tax collection.

It said taxpayers engaged in criminal activity, under investigation or being audited by the ATO were excluded from the amnesty program, called Project Do It.