As Of refers to the date that the report will capture transactions. If As Of is set to yesterday, then the transactions that the Aging report will include will be all the transactions dated up to yesterday’s date.
Age As Of refers to the date from which the report will count the age of transactions. If Age As Of is set to today, then the age will be based on a count including the date today.
Example:
Age As Of = June 15, 2021
As Of = July 1, 2021;
Date of Bill 1 = June 1, 2021
Date of Bill 2 = July 1, 2021
From the example above, the age of Bill 1 will be 14 days and Bill 2 will be -16. Take note that the Age As Of does not necessarily follow the As Of date unless you change it.