The Finance Minister Bill English has left open the option of introducing a capital gains tax and changes to GST.
Addressing the National Party's annual conference in Christchurch, Mr English said it would take a lot to convince the Government to follow that course but that everything was on the table.
Mr English said changing the tax system is one of the reforms needed to lift the country's economic performance, but it will carry political risk.
Later he told reporters the Government was open to a wide debate and isn't ruling anything out.
"We've set up a tax working group, which is doing a bit of a first principles look at the tax system - quite similar to the Australian review, but we're not pre-judging any of the issues.
"We don't want to go around stopping people from thinking about it."
Mr English says it's important to obtain the views of National Party members before any decisions are made on tax.
"Remarkable" year - Key
National's annual conference started in Christchurch on Saturday morning, with almost 700 delegates, MPs and observers in attendance.
Prime Minister John Key says the conference is an opportunity to reflect on a remarkable 12 months for the party.
He says National has earned the right to be in government, but there is no doubt it has taken power at a difficult time for New Zealand.
Health and education
Health Minister Tony Ryall has told the conference the Government will be able to report within the next month that the country has had the "single biggest increase in elective surgery over a six month period ever".
He says the Government is stripping the bureaucracy from the health system and focussing on delivering good services.
Education Minister Anne Tolley says will not stop the introduction of national standards in primary schools.
Speaking at the conference, Mrs Tolley says the Government will introduce national standards for literacy and numeracy so that parents can get plain English reports on the progress of their children.
Deputy Prime Minister Bill English's address to the conference on Saturday afternoon will focus on the economy and the impact of the recession.
New board members elected
National Party members have elected five new board members, from among eight contenders.
The successful candidates were Alastair Bell, Kate Hazlett, Grant McCallum, Pat Seymour and Scott Seymour.
Wira Gardiner, who will accept a knighthood in two weeks, missed out being elected, as did Dennis Catchpole and Bruce Mills.
Delegates have farewelled outgoing president Judy Kirk, who reminded delegates that the only thing that counts in an MMP election is the party vote.
On Sunday, the board will select a new party president from within its ranks, as Ms Kirk steps down after seven years in the role.
She said the party has worked hard to build itself again since a resounding defeat in 2002, when it won only 21% of the vote.