Will old rent payments be reported retroactively?
Retroactive reporting, if offered, depends on what payment history is available and verified at the time of enrollment — check the enrollment flow for what’s included.
From the guide Rent-Payment Credit Reporting.
Roommates who split the rent
When rent is split between roommates, each roommate’s share is its own charge under that roommate’s own name. A roommate who opts in has only their own share reported, and one roommate’s late share is never reported against another.
Read the whole guide: Rent-Payment Credit Reporting