@gregg_appcoll Understood about the privacy issues--if the addendum feature could be added, that would be great and honestly seems like it would address most of the issues.
Ideally it would be implemented in a way that allowed for admins to specify one or more individuals that should receive the email warning, and to specify when it was sent (it would be great it if it could be a) when a contact record with an unlisted customer number is saved and b) on a regular scheduled basis, e.g., on the 1st of each month).
Although, it seems like the automated approach could be implemented, but with a check to make it so that if there are two accounts listing the same customer number, then permission is sought from the first before authorizing the second. I mean, if I enter another customer's customer number into the settings page and save it, it's still there, right? You just don't enable it until permission is granted?