Help? Tenants asking to change to Permitted Occupiers to help with housing benefit???

[westminster]

If you have them all named on the same joint tenancy, and one wants to leave, they have to give you formal notice, and that ends the tenancy for all of them.

To clarify for OP, this only applies during a periodic tenancy. During the fixed term, the tenant(s) cannot give notice to end the tenancy (not unless there is a break clause, in which case all the joint tenants would have to jointly serve notice under the break clause).