Do you keep copies of all the letters sent as part of your reg D excessive transaction monitoring program or do you just document that a letter was sent?

We keep copies, but our volume is low. I don't believe there is a record retention requirement but you do want to document in some fashion that appropriate action has been taken when excessive transactions occur.

I would accept a log that included what standard letter in your series was sent, the date, address and any response from the customer. Using this log you could more efficiently look for past occurrences in a running 12-month period, versus looking for a customers file and seeing what/when the last activity was.