Voting in the contest to replace Jeremy Corbyn as Labour leader ends later, ahead of the result on Saturday.
Labour members have until 12:00 BST to choose between Rebecca Long-Bailey, Lisa Nandy and Sir Keir Starmer.
The party is also electing a new deputy leader, following Tom Watson’s resignation in December.
It is understood members will hear the result via email and the media after a special conference was cancelled over the coronavirus outbreak.
Mrs Long-Bailey confirmed earlier this week that the candidates had been asked to record a victory speech “so it can be sent out over the airwaves as quickly as possible”.
Voting began on 24 February.
Among those taking part were 114,000 new members who had joined since December’s election, where Labour won its lowest number of seats since 1935.
Members of affiliated trades unions and groups have also been voting, as well as about 14,700 “registered supporters” who paid £25 to take part on a one-off basis.
Those eligible have been voting via email if they have registered an email address with the party, or via a postal ballot delivered to their home.
Voting works using a preferential system, with members ranking the candidates in order of preference.
If one fails to get more than half the first preference votes, the second preference votes of the lowest-ranked candidate are redistributed until the contest produces a winner.
The system is the same for the deputy leadership race, where shadow education secretary Angela Rayner is regarded as the front-runner.
Shadow equalities minister Dawn Butler, Scotland’s only remaining Labour MP Ian Murray, Tooting MP Rosena Allin-Khan and shadow justice secretary Richard Burgon are also in the running for the role.