The Conservative Party says its new leader will be declared by 6 December, ending speculation of the timescale of the contest.
Michael Howard will stay on as caretaker leader
The party has announced that nominations for candidates for an MPs' vote will start on 7 October.
Party members will have the final vote of the remaining two candidates, after at least three ballots are held.
Michael Howard will stand down after next week's party conference, but is to remain as caretaker leader.
An attempt by Mr Howard to change the rules on who chooses the next leader was defeated on Wednesday in a vote of MPs and senior party activists.
It means now that, while MPs will vote in the initial ballots, all party members will get to choose between last two candidates.
All 198 Tory MPs can vote - the first ballot will take place on Tuesday 18 October, the party confirmed.
The candidate with the least number of votes will be eliminated.
A second ballot will then take place on Thursday 20 October - and again the candidate with the least number of votes will be eliminated.
The remaining candidates will face a third ballot on Tuesday 25 October and this process can continue every Tuesday and Thursday until only two candidates are remaining.
The two remaining candidates will then face a ballot of all Conservative Party members, believed to be around 300,000 in number.
This will close on 5 December with the result being announced the next day.
The announcement on Thursday came as two candidates for the leadership, David Davis and David Cameron launched their respective campaigns on Thursday.
Others who have so far declared their intention to stand are Sir Malcolm Rifkind, Kenneth Clarke and Liam Fox.