I'm only going to be partially helpful.
You need to start by defining exactly what you mean by "taken". You might want to look at - Using_Course_completion
There is an optional report that looks like it might help, but I haven't used it personally - https://moodle.org/plugins/report_completionoverview
Hi Howard -
Thanks for the response. By have "taken" a course I mean a user has completed 100% of the course. I am searching for reporting that shows when the user completed the course 100%, as well as every time that user has completed the course. The idea is that this course in particular is an annual training course, and for system admins to have a full log of all of the history.
From what I can see the reports just log the most recent time a user has completed a course. The most recent course completion seems to overwrite the previous course completion.
Again, thanks for the help. I'll keep looking around.