OTTAWA — The Liberals will choose a new leader Sunday, marking the end of Justin Trudeau’s decade as prime minister.

He will step down officially in the days to come. On Tuesday, Trudeau said he will have a conversation with the incoming leader to determine exactly when that will happen.

“It should happen reasonably quickly, but there’s a lot of things to do in a transition like this, particularly in this complicated time in the world,” Trudeau said.

Here’s a look at what comes next.

The handover

First, Trudeau needs to formally resign as prime minister. He’ll meet with Gov. Gen. Mary Simon and, on his advice, Simon will invite the new Liberal leader to form a government.

That could happen right away, said David Zussman, an adjunct professor in the school of public administration at the University of Victoria who has written a book about political transitions. Or it could take days, or weeks.

“Justin Trudeau could, in fact, be sitting in his seat in the House of Commons when the House comes back at the end of March,” he said.

But that seems unlikely.

On Thursday, Trudeau insisted he does not plan to stay on in a caretaker role during the next election.

The new leader is likely to want to get started soon, Zussman said.

Forming a government

The new leader needs to name a cabinet and set a date to swear them in.

Trudeau’s cabinet has 37 members. Some ministers could stay on, or there could be new faces around the table from the Liberal caucus.

Michael Wernick, the former clerk of the privy council, said the new leader has “what the hockey coaches call a short bench” because so many Liberal MPs have decided not to run in the next election.

He suggested a smaller cabinet is likely, with some ministers carrying more than one portfolio.

Zussman said keeping some of the same ministers makes things simple for the public service.

New ministers need to be vetted and set up with things like security and secure phones, drivers and cars.

And everyone has to get up to speed on their files — quickly — because an election is coming in the next six months.

Naming a team

Another team needs to be named quickly: the Prime Minister’s Office staff and key advisers.

New people coming into top staff jobs need security clearances and briefings to get up to speed.

And at least part of the new leader’s inner circle will have to have eyes on the next election, which the leader could call at any point once the cabinet is named.