Letter to college from office (for permission of absence) where I am working while studying MBA

I'm working in an office as well as studying MBA. So I'm not attending college as I'm doing my job. My college authority has asked me to bring a letter from the office to give permission and record attendance. Please suggest what content should be included in the letter.

Nothing much, just a certification from your company that you are working with them. It covers details like Date of joining, department, post. It should be on the letterhead of the company.