Good Lawyer Guide's response

You must give written notice to your landlord but you may not be able to end your agreement early if you signed a tenancy for a fixed term. If you are in a fixed term, check your tenancy agreement to see if it has a break clause that will allow you to end the tenancy earlier. Otherwise, talk to your landlord to see if you can negotiate an early release from your agreement. If your landlord will not agree, you can still leave early but you could be liable for the full rent still owing. Sometimes it’s possible to negotiate a partial payment of outstanding rent.

If you are in a periodic tenancy you must normally give at least four weeks’ notice and try to ensure it ends on the first or last day of the tenancy period.