Your landlord must follow a legal process to bring your tenancy to an end. Most private tenants have an Assured Shorthold Tenancy which requires the landlord to issue either a Section 21 or a Section 8 notice.
This type of notice must give you at least 2 months notice but the landlord does not have to give a reason for asking you to leave. If your tenancy started after 1 October 2015 notice must be given using the Notice Seeking Possession.
You can be given a Section 8 notice at any time if any of the following apply:
The notice period can be as little as 14 days.
You can submit a defence form to the court if you have been served a Section 8 notice.
A landlord cannot force you to leave when the notice expires but must first gain a court order.
To find out if a notice you have been given is valid visit Shelter (requires a login)