This is a Section 21 Notice.
A ‘Section 21 Notice to Quit’, so called because it operates under section 21 of the Housing Act 1988, is the notice a landlord can give to a tenant to regain possession of a property at the end of an Assured Shorthold Tenancy (AST). The landlord is able to issue the tenant with a section 21 notice without giving any reason for ending the tenancy agreement.
A landlord has the legal right to retain possession at the end of a tenancy but must follow the correct legal procedure, which includes serving a section 21 notice. The Housing Act 1996 amended the section 21 of the 1988 Act by requiring this notice to be given in writing.