Such as for NHS workers, teachers, police, firefighters, the armed forces and some other public sector workers who have unfunded schemes.
If there are going to be any charges to leave your scheme then the transfer will not go ahead automatically in under 12 days.
For this you need to take advice as you could be giving up life long benefits that need proper consideration.
Some schemes have guaranteed annuity rates or other special circumstances where you need to understand more about what you are giving up before you transfer.
If your employer is still paying into the scheme then it's not possible to transfer out until they stop.