Researchers behind a Victoria University study have been surprised by the extent to which women, over their life cycle, pay less tax than men.
The paper which examined taxation and government welfare spending in New Zealand also found women receive more government payments than men.
Researcher Professor Norman Gemmell said it had the effect of reducing income inequality between the genders.
He said there were a number of reasons, including that women lived longer than men.
"Because they're experiencing the longer period of pension age and they're going to receive more pensions.
"And another reason is that women tend to spend more time out of the labour force than men, so they're not earning income in the labour market, so they'll not be paying tax."
He said projections that more women and those over 65-years-old would participate in the labour force over the next 50 years could have implications.