The Greens say they can meet all their policy promises and still run budget surpluses.
They've put all their election policies together in a single document and it's been checked out by Infometrics, an independent economic consultant.
"This fiscal plan ties together everything we've promised this year and provides the substance that makes the Green Party's promises 100 per cent credible," said party leader James Shaw.
"Think of this as a solid business case for where New Zealand should be heading, and an independently audited plan to get there."
The fiscal plan document says Infometrics has found that the Greens will run surpluses over the next three years, slightly smaller than those outlined in the Pre-election Economic and Fiscal Update (PREFU).
PREFU forecast surpluses of $2.9 billion, $3.5b and 5.7b for the next three years.
The fiscal plan says the Greens will be able to take "significant steps" in the first parliamentary term to address child poverty, make lakes and rivers swimmable and tackle climate change.
"We can meet these challenges while being fiscally responsible by raising some new revenues," the document says.
"For example, through a new, comprehensive capital gains tax - excluding the family home - and by finding savings from low-value government spending."
That's where the plan runs into a problem, because the only way the Greens can get into government is by going into coalition with Labour which has ruled out any new taxes in its first term.
The fiscal plan sets out in detail, and confirms, all the Greens' previously announced policies.
It sets the 2050 goal for a carbon-neutral economy - the same as Labour's - and 100 per cent renewable energy by 2030.
It would invest $11 billion in clean, safe, rapid transport over the next decade, put $100 million into Kiwibank to help it expand into commercial banking and give tax breaks for electric vehicles.
It would put a levy on nitrate pollution from agriculture, double the number of conservation rangers, and put a charge of 10 cents a litre on exported bottled water.
The bottom tax rate would be reduced from 10.5 per cent to 9 per cent on income under $14,000, and there would be a new top tax rate of 40 per cent on income over $150,000 a year.
Health and education funding would be returned to "real levels" at the same rate Labour is promising.