All tenancies come to an end. If you have given your tenant a fixed term (of 6 months, a year or any other agreed duration), that tenancy will automatically end at midnight on the last day of the fixed term. In the vast majority of cases - and in particular, if the tenancy is an AST - if the tenants remain in the property after the fixed term has ended, a new ‘periodic’ tenancy will arise automatically. For ASTs this will be under section 5 of the Housing Act 1988. You don’t have to do anything to make it happen. For example, there is no need to sign any new documentation, it will just happen if the tenants are still there after the fixed term ends. Bearing this in mind, you should review all your tenancies a few months before the fixed term is due to end. In normal times this would be two months before, as that is the notice period for a section 21 notice if you want them to leave. This is not the case at the time of writing (the section 21 notice has a notice period just now of six months). However, notwithstanding this, two months before the end of a tenancy agreement is still a good time to review your tenancies.