The timetable for the contest to succeed Jeremy Corbyn was agreed at a meeting of the party's ruling National Executive Committee (NEC).
A party spokeswoman said that the postal ballot of members will run from February 21 to April 2.
Under the terms of the contest, candidates need to secure the nominations of least 10% (22) of the party's MPs and MEPs.
Those who succeed will then go forward to the second stage when they must get the nominations of 5% of all constituency Labour parties or three Labour affiliates - of which at least two must be trade unions - comprising at least 5% of the fully paid-up affiliate membership.
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The freeze date for new members to join and be eligible to vote will be January 20 in the postal ballot.
This marks a change from the last election in 2016 when a retrospective cut-off date was set.
The party said the alteration was intended to ensure the election was as "open and democratic as possible".
As in 2016, people will be able to join as a registered supporter for a fee of £25 provided they are on the electoral register and meet the membership qualification criteria of membership of the party.
The same rules and timetable will apply to the contest to succeed Tom Watson as deputy leader.
Under the timetable set out by the NEC, nominations from MPs and MEPs will open on January 7, closing at 2.30pm on January 13.
The second stage of nominations from constituency parties and affiliates then opens on January 15 and runs to February 14.
The ballot of members and registered supporters opens the following week on February 21, closing at midday on Thursday April 2.
Applications to become a registered supporter open at 5pm on January 14 and close at 5pm on January 16.
So far five candidates have announced they intend to stand for the leadership - frontbenchers Sir Keir Starmer, Emily Thornberry and Clive Lewis, and backbenchers Jess Phillips and Lisa Nandy.
Shadow business secretary Rebecca Long-Bailey is also widely expected to run.