That's an increase of A$984,496, just over NZ$1m, or nearly 42 per cent.
Mentis' cash salary increased from A$1.34m to A$1.44m during the year although her non-monetary benefits fell from A$261,177 to A$238,391.
It was a cash bonus that made all the difference, with her receiving an extra A$893,340 in FY21. That was the second highest cash bonus behind NAB group chief executive Ross McEwan's A$1.5m cash bonus.
He had a total remuneration package of $5.29m, up from A$2.3m.
A BNZ spokesman said Mentis received zero short term incentive payments for both 2020 and 2019.
"This was to reflect the difficult and uncertain situation faced by our customers as the pandemic broke out in 2020, and that in 2019, despite BNZ having a solid year, NAB had not achieved benchmarks on some financial and non-financial results."
The spokesman said as far as it knew BNZ was the only bank in New Zealand to have no short term incentives for its entire executive team last year because of the pandemic.
"This will affect comparisons across time, but the resumption of the short term incentive is reflective of the complexity of her role as CEO, the strong result BNZ has achieved, and her leadership and performance overall."
Mentis' remuneration well exceeded that of rival ANZ NZ CEO Antonia Watson, who heads up New Zealand's largest bank by assets.
Watson's remuneration hit $2.54 million (A$2.44m) in the year to September 30, up from $1.87m (A$1.79m) in the 2020 full year.
Former Westpac New Zealand chief executive David McLean also received a substantial boost to his pay packet on retirement this year.
McLean officially retired on June 25. For the year to September 2021, his total remuneration was A$2.99m or $3.11m. That compares to the prior year when it was A$1.59m or $1.66m.