If a tenancy is coming to the end of its fixed term, one option is for a new tenancy to be created (a renewal) with a new fixed term, tenancy agreement and potentially new rent amount.
To create a renewal, go the the dashboard page for the letting and click the "Create Renewal" button in the middle of the screen:
Amend the term, rent, fees as required.
A new letting will be created, but linked to the previous letting so that the deposit is carried forward. The letting details page provides a link to the previous letting:
If there was a negative balance on the last landlord statement in the original tenancy, this is also carried forward to the opening balance of the first statement in the renewal.