Hi,
Usually, an individual's share from the jointly owned property will be included as part of their personal rental business profit. Individuals who have jointly owned property should know who is keeping the records and have access to them. They are personally responsible for including their share of the income in their own tax return even if they agree that someone else will keep the records.
In this case, income, and expenses, received to mid September is split 3 ways and thereafter in 2 ways. Further information is available here:
PIM1030 - Introduction: jointly owned property & partnerships
Thank you.