People 18YO or older in Aotearoa New Zealand can still enrol to vote, even on voting day itself (14 October 2023). Enrolling earlier helps get a person on the printed roll but special votes on the day may still be counted.
https://www.rnz.co.nz/news/national/498811/first-time-eligible-voters-weigh-in-on-the-pressure-to-decide 

It may take a few clicks but the official Electoral site has information and options for #HowToEnrolToVote 
https://vote.nz/enrolling/get-ready-to-enrol/are-you-eligible-to-enrol-and-vote/