We refer to changes of tenancy as Moves.
When you know a tenancy is coming to an end (e.g. when a tenant serves notice) you should schedule a Move Out. You can future date a Move Out up to 12 months in advance.
When you know a new tenancy is about to begin (e.g. when a tenant signs a new tenancy agreement) you should schedule a Move In. You can future date a Move In up to 12 months in advance.
If you are instructed on a new property and it is vacant when you receive it, you should add a Move Out straight away. If you don't know the exact date it became vacant then you should just use the date you received it as a vacant property.
NOTE: if you know a Move Out date and a new Move In date coming up for the same property, the portal will allow you to add both at the same time so this saves you a job of having to add it at a later date.