The next leader of the Labour Party will be announced on April 4, the party's National Executive Committee (NEC) has agreed, with the race set to officially get underway tomorrow (January 7).
The meeting agreed a timetable for the leadership election and discussed whether to change any of the rules to a contest that saw outgoing leader Jeremy Corbyn elected twice.
MPs who want to succeed Mr Corbyn as Labour leader will have one week from January 7 to announce whether they will run, and to secure nominations from MPs and MEPs - of which they need 10% to get on the ballot.
If candidates get the required 22 signatures by January 13, they will then need to gain backing from Constituency Labour Parties (CLP) and unions, where they will need 5% from either.
Once prospective leaders have been nominated by their colleagues, a new wave of Labour Party registered supporters will be allowed to join the election process from January 14 - 16.
ITV News Political Correspondent Paul Brand explains the contest:
Anyone who wants to back a candidate, but is not already a full member of the Labour Party, will be allowed to pay a fee of £25 to register themselves as supporters and they will be given 48 hours to register to vote in the contest.
From January 15 until February 14 CLPs and unions will be able to nominate who they want to be the next leader.
On January 20 there will be a freeze on new members' voting rights, meaning anyone opting for full membership after this date won't be able to vote in the election.
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".
The postal ballot of members will then run from February 21 to April 2 with the result being announced two days later on Saturday April 4.
"We are by far the largest political party in the UK with well over half a million members," a spokeswoman said.
"We want as many of our members and supporters to take part, so it has been designed to be open, fair and democratic."
The same rules and timetable will apply to the contest to succeed Tom Watson as deputy leader.
ITV News Political Correspondent Paul Brand, who has spoken to NEC members inside the meeting, revealed current leader Corbyn wanted the 'registered voters' fee lowering to £12.
Paul says it suggests Mr Corbyn "believes there is still untapped enthusiasm" for his style of politics and wants those who back his policies to be able to vote more cheaply.
In theory, Paul says, those voters would back "the left's preferred candidate (probably Rebecca Long-Bailey)".
An NEC member also told Paul the group agreed "extra checks to make sure people don't register their dogs this time."
While Paul says most candidates seem "fairly content" with the timetable, there is a theory that it favours candidates backed by left-wing group Momentum.
There was reportedly a row at the NEC over membership data, which is being withheld from candidates until they receive the required amount of nominations.
It means any candidate backed by Momentum will have access to their data before the others.
Several Labour MPs have already announced their intention to run the contest, but more race entries are expected.
One MP almost certain to announce her bid to lead the party is shadow business secretary and ally of Mr Corbyn, Rebecca Long-Bailey.
Earlier on Monday shadow education secretary Angela Rayner, when revealing she would run for deputy, said she would back her "friend" and flatmate Ms Long-Bailey in the contest, if she runs.
If Ms Long-Bailey does join the leadership contest, she will face competition from Birmingham backbencher Jess Phillips, shadow Brexit secretary Sir Keir Starmer, Wigan MP Lisa Nandy, shadow treasury minister Clive Lewis and shadow foreign secretary Emily Thornberry.
Other Labour MPs have said they are considering a bid for the leadership, including party chairman Ian Lavery.
Mr Lavery, on his way to the NEC meeting, told ITV News Political Correspondent Paul Brand he is "going to wait and see what happens" before he decides whether to join the race.
"We’ll take everything as it goes," he added.