It can be a fraught political process, ranking incumbent MPs and any aspiring members of parliament on the party list.
The list determines placing for MPs and candidates, for those who don't end up winning an electorate seat.
Labour secured 65 seats in the 2020 landslide, but on current polling could lose about 20 MPs.
Labour's list for the 2023 election was revealed today and there's not too many surprises, which is notable in itself.
Our political editor Jane Patterson joins us now from our Parliament studio.
