I think it should not be financial year if you can show 24 months income if your income is monthly salary.
Does this help?
35061 (2019). Stuart Smith to the Immigration (Minister - Iain Lees-Galloway) (10 Oct 2019): Will sponsors be required to provide evidence of their annual income through Inland Revenue tax statements after a Parent Resident Visa application is lodged?
Hon Iain Lees-Galloway (Immigration (Minister - Iain Lees-Galloway)) replied: Yes.
https://www.parliament.nz/en/pb/orde...ation-minister