There are two main ways of repossessing property let under an AST under the Housing Act 1988:
a section 21 notice
a section 8 notice
If you want to regain possession of the property on a no-fault basis you need to serve a section 21 notice. This notice is used to regain possession of the property. You don't need to have reasons for wanting the property back. This is the simplest way to get the property back.
If the tenant and property are located in England you should use a Section 21 (Form 6A) notice in England. For more information on the section 21 procedure in England, read Repossessing property - section 21 notices.
A Section 8 notice can be served during the fixed term where reasons (known as 'grounds') for possession exist (eg the tenant regularly pays the rent late). A section 8 notice is served when the tenant has breached the tenancy by not paying the rent or by not repairing the property, for example. For more information, read Repossessing property - section 8 notices.