Finance Minister Bill English is preparing to present another tight budget with new spending for health, education and welfare coming from savings shaved off other departments.
He's also going to announce on Thursday changes to tax rules which he is describing as "patching up some holes" in the system.
It will be his second zero budget in a row, with little or no new money in it as the government struggles to get on top of debt and return to surplus in 2014/15.
Tobacco excise will push up the price of cigarettes, and a previously announced regime for student loan repayments will also deliver extra revenue.
Liquor could also cost more after Thursday but that can't be confirmed.
Prime Minister John Key says tax changes involve "one or two adjustments - it isn't anything too scary".
He isn't giving much away and said in his final pre-budget comments on Wednesday there will be "one or two surprises but there's not going to be anything dramatic".
Mr English told parliament the budget would invest significantly in infrastructure, skills and innovation.
"It will build a stronger, more competitive economy," he said.
Opposition parties are warning there will be a raft of cuts spread across departments as the government puts more money into voter-friendly areas like more operations and faster cancer treatment.
They don't think the budget is going to have anything in it to generate economic growth and create jobs.
Labour's finance spokesman, David Parker, says consecutive zero budgets are proof of failure.
Mr English says it's the responsible way to deal with an economy that's been under stress because of the international financial crisis and the Christchurch earthquake which is costing the government nearly $6 billion.