Do we have to allocate players to a team from the start of the season?

The first/second week in September we don't have a full book of players and changes are huge in terms of team selection in the first few weeks. If when a player applies to join our club we then allocate a team, can this be edited or changed before the first league game Squad allocations can be amended at any time, so there is no issue with adjusting allocations during the season.