Treasury estimates it could cost up to $5 billion to pay for the overseas carbon credits New Zealand needs to honour its Paris Agreement commitments.
An additional $1.6 billion may also be needed to pay for credits to meet a subsequent commitment, due by 2035.
Treasury said the figures did not reflect any government intentions or decisions, but was publishing them so there was transparency over possible future costs.
New Zealand has the option of meeting its pledge to halve net greenhouse gas emissions by 2030 entirely with domestic policies.
However, the most recent analysis from the Ministry for the Environment showed that there was a shortfall of 84 million tonnes of emissions, that would need to be made up by paying other countries to offset their emissions instead.
