How do you track arrears by month?

Currently trying to understand how you all are tracking your collections % by month? Typically, we are seeing tenants throughout our buildings lagging behind on payments right now; we will typically end a month at ~80-85% collected. However, we are unable to find a way to accurately track when / how long these balances are taking to be repaid.

It appears that Yardi can produce a simple report for one month in particular, but when you want to understand collections data (%) for prior months, the entire system is incapable of producing this. I've spoken at length with Yardi on this as well, and none of their reps know how to do this. Any idea how you all are doing this?

Thanks!