Nominations for the position of Labour Party leader must be received by 9am Saturday and if there is only one nominee, that person's name will be made public.
If there are more than one, the names will remain secret ahead of the voting process that then has to be run by the caucus, the Labour Party announced as the party rushes to replace resigning Prime Minister Jacinda Ardern.
Nominations need the support of at least 10 percent of the caucus, which in this case is seven MPs - not including the nominee.
At the Sunday meeting at 1pm, if there is only one nominee, an endorsement by caucus is required.
Members unable to attend in person can vote by proxy.
Chief Whip Duncan Webb is the returning officer for this election.
There will be an exhaustive ballot, which means the vote will be by rounds and the lowest polling candidate will be removed at the end of each round.
Webb said this would continue until either one candidate had two-thirds of the vote or more, or there were two candidates and neither could secure two-thirds of the vote.
There are no limits on the number of votes to be taken.
Webb said because caucus had seven days from the date of resignation to reach a decision, a leader could be chosen with the support of at least 66 percent, or about two-thirds, of the caucus.
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