On the tenant details screen you can specify a tenancy end date. Up until now, when that date is reached the tenant automatically went into a closed state.
Now there is an option to over-ride this default behaviour and allow the tenant to remain open even after their end date can passed. This means the tenant will continue to accumulate rent owing. If you choose this option, it is your responsibility to make sure you close the tenant when required.
This new option is found on the Functions/Setup/Options/Features tab. The default setting is for tenants to continue to be closed at the end date.