Important information that should be in an internship offer letter. Gov or apply via Careers.Ohio.For autumn offers: Please give students a minimum of 3 weeks from the time of offer or until November 1st, whichever comes later, to make a decision. Be sure the letter of interest includes dates of availability and reason for interest in the organization. I obviously don't want to be in a situation where I would have to back out but does anyone have experience with accepting offers and backing out later? You're doing the work. An internship letter is an official document a company provides to a potential candidate for an internship position. Once you receive your official offer letter, you must complete the steps below: Complete and turn in your new hire HR paperwork. However you mention "someone in a company". For a student to enroll in the appropriate college course (internship or co-op), please send the student a formal offer letter.