Every term, a handful of students tells me that they have professional obligations that will require them to miss a class meeting. They may be going to job interviews, career fairs, internship interviews, conferences, and so forth. Sometimes they have university documentation (like a letter from an advisor in their majors). Just as often, however, they do not.
To ask them for some documentation on their activities, I developed Trip Report Assignments, which ask students to report on where they went and what they did there.
In the end, I allow the trip report assignments to count for missing class work, and I feel more certain that they actually went on the trips that they tell me about. Naturally there are some limits. I use these trip reports as an exception for specific situations. I wouldn’t allow students to make up a dozen classes with trip reports, but in the situation where a student is going to miss one or two classes for a professional event, they work well.