National is convinced one of the proposed taxes to help pay for its fiscal policy wouldn't break international law.
For example, Article 24 of New Zealand's double taxation treaty with China - signed in 2019 - clearly states Aotearoa can't tax Chinese buyers more than Kiwis.
"They have missed this very black-and-white rule that we have in that tax treaty," Labour's David Parker said on Thursday.
Despite this, however, National's Paul Goldsmith believed the policy would get across the line.
"We can find a way through, other equivalent places like Australia and Vancouver and places have these taxes - and all we're trying to do there is gain a bit of extra revenue to give some relief to the squeezed middle," he told AM.
The levy aimed to raise $740 million to contribute to National's $14.6 billion tax relief plan.
Labour and others have criticised National's plan, which could see families without children earning less than $120,000 getting an extra $100 in their pocket each fortnight, which extended to $250 every two weeks for those with children.
National has accused the incumbent Labour Government of not doing enough for the "squeezed middle", which is the catch-cry at the forefront of the policy.
On Friday, senior National MP Goldsmith reiterated the party's finance spokesperson Nicola Willis had received independent advice from both legal and tax experts on the policy.
"We won't be breaching any law," said Goldsmith, National's Justice spokesperson. "We're very confident that we're going to be able to raise those funds.
"It's a complex area of law and we've had the advice that we can do it, and we are going to do it."