The Government is struggling to work out how its proposed tax cuts could benefit low income families who pay no tax at all.
The Tax Working Group has suggested cutting personal income tax rates but offsetting that by introducing a land tax, raising GST or getting tougher on gains from property investment.
Prime Minister John Key will not be drawn on what changes National might make to the tax system, but says any changes have to be fair to all taxpayers.
But because about 40% of families pay no tax, he says it is difficult to work out how tax cuts might benefit them.
Mr Key will signal the Government's intentions on tax when he delivers the Prime Minister's Statement to Parliament next Tuesday.
Full details of the tax package won't be known until Finance Minister Bill English delivers his second Budget on 20 May.
