A fixed-term tenancy of 90 days or less is called a short fixed-term tenancy. If a short fixed-term tenancy comes to an end, it doesn’t automatically become a periodic tenancy. The tenancy will end and the tenant has to move out, unless they come to an agreement with the landlord.
If you’re a tenant of a myRent tenancy you can generate and send an end of tenancy notice if eligible by following the steps here
You can find more about ending a tenancy here