FACTBOX-What's next in process to replace UK PM Boris Johnson?

Boris Johnson is stepping down as British prime minister, forcing the ruling Conservative Party to choose a new leader who will be announced on Sept. JULY-SEPTEMBER - THE RUN-OFF The two candidates campaign and hold hustings among party members to win their votes.

Boris Johnson is stepping down as British prime minister, forcing the ruling Conservative Party to choose a new leader who will be announced on Sept. 5.

The winner will inherit a parliamentary majority and will become the next prime minister. WEDNESDAY JULY 20 - FINAL SELECTION BALLOT

Conservative members of parliament chose former finance minister Rishi Sunak and Foreign Secretary Liz Truss to go through to the final stage - a vote by around 200,000 party members. JULY-SEPTEMBER - THE RUN-OFF

The two candidates campaign and hold hustings among party members to win their votes. Members can vote by post or online, with the last vote received the one that counts if there is any duplication. Ballots must be received by 1600 GMT on Sept. 2. SEPT. 5 - NEW PRIME MINISTER ANNOUNCED

The party announces who has been elected by members as the new leader. The candidate with the most votes wins. SEPT. 6 - JOHNSON HEADS TO THE PALACE TO RESIGN

Johnson is expected to leave office on Sept. 6, his spokesman said, adding that he would go to Buckingham Palace to tender his resignation to Queen Elizabeth.