Aging 

In the Main Menu, select Tools | Calculate Aging. The following window will appear:

Aging is usually run daily for most offices, but you do have the option of running it monthly instead.  If you want to run it monthly, go to Setup | Misc, and check that option.  This will have a couple of consequences:
1. When you open a patient Account, the aging will be automatically calculated as of the last calculated date rather than the current date.
2. When you do calculate aging from the window above, you will have to manually change the date to the one that you want. You would typically be doing this on or near the first of each month, and you would change the date to be exactly the first of the month.  If you try to click OK without first changing the date, it will warn you that the date is the same as the previous date.

You will be prompted to calculate aging if you try to run Billing or run Finance Charges and the aging has not been caculated for today's date.  Once the aging has been calculated, the date is stored in the database for reference.

You can run an Aging Report and a Payment Plan report to see the results.