Finance Minister Steven Joyce has hinted National is thinking of going into the campaign on a platform of further tax cuts for those on middle and high incomes.
National delivered a $2 billion a year package of tax cuts of up to $20 a week in the Budget this week by shifting the two bottom thresholds.
Joyce also said he was keen to deliver further cuts as fiscal conditions allowed - and on Friday Joyce would not rule out taking that to the polls as early as the election.
He said National had made it clear they would like to make further tax cut moves when it could.
"It's just a matter of on what basis and what we'd do. We haven't talked about it yet, but that's something we might talk a bit more about before the election - we'll just wait and see.
The Government has lots of decisions to make in terms of what it will be campaigning on."
Labour and the Greens have both criticised the tax changes in the Budget, which lifted the two bottom thresholds from $14,000 to $22,000 and from $48,000 to $52,000.
Legislation to introduce the Budget's Families Package passed in Parliament on Friday with support from all parties other than Labour.
Labour leader Andrew Little said the increases in Working for Families did not go far enough and the tax cuts delivered more to high income households than to those on low incomes.
Labour would present its own rival families package before the election.
Joyce said the Family Income package used up most the headroom in the books for the next four years, so any parties making expensive promises would have to set out how they would pay for it.
"I think it's a test for everybody actually, including ourselves, if you're going to suggest doing other things, what wouldn't you do and that's going to be an interesting part of the campaign."
The thresholds have not changed since 2010.
National's past three Budget have focused on delivering to low income families through the $25 increase in the benefit for those with children in 2015, the Vulnerable Childrens' package in 2016 and the Family Incomes package this year.
That prompted some, including the Taxpayers' Union and Act, to call for more for middle and higher income families by changing the tax thresholds.
The Government did not shift the next thresholds despite acknowledging concern that the average wage was rapidly closing in on the higher 33 per cent tax rate for income above $70,000 a year, so would be affecting more and more middle income earners.
The Families Package will cost $6.5 billion over four years and was on top of National's self-imposed $1.5 billion operations funding cap for new spending initiatives.
Joyce said the allowance was "a construct" which was intended to ensure the Government had the discipline to stay within a spending envelope.
"So the decision is we knew we had a bit more room as a result of the growth we've seen.
So we took the decision that rather than saying the Families Income package had to be in the operations allowance, it couldn't be, that we'd do that separately."
He denied that meant it was effectively meaningless if National could just ignore it.
"It is a really important discipline and we intend to stick with it. We've never said the tax packages if we do them would be within the allowance."