Hi @ncassella although you can import a CSV list to enrol users, you cannot add the completion date using the CSV import. This can only be done manually or using an API to load the records.
If you're not bothered with tracking what session they were/are enrolled in, I think you can do your tracking on the Enrolments tab of your ILT course and then change their status to completed. Depending on how many users you are tracking, you could change the status of several hundred users at once however they will be tracked with the same date. you can also change this but it’s likely to be quite the manual effort.
@ncassella Additionally, you may have a lot of issues trying to assign a completion date in the past. When we tried to do this several years ago, the API import would default to the creation date of the course. We eventually solved the problem (kinda) by asking our AM to do a manual import for us as part of our initial implementation. It was very messy.