I don't think a letter is appropriate in this situation. Always talk to the person in charge personally. It's easier to resolve issues in person, and letters are the cowards way out. It's not professional and can't explain what you really want to say. It takes guts to do this in person and the manager will appreciate it more.
sample of an explanation letter
explanation letter for family problem
how do u write explanation of a surname change
Honestly.
You do not need to write an explanation letter. It is better not to make any waves and just go along with the new policy. If you need to fight this, you should talk directly to HR or your boss.
To write an explanation answer letter of why you were AWOL you should include your name, rank, and specifically why you weren't on duty. You can start the letter with," please accept this as written notification as to why I was AWOL."
you vomited in the locker room sink
You can write a letter of explanation to an immigration officer to accompany an application of reinstatement by aquiring the official documentation and then filling it out.
If you are asking about a school in the United States all you need to do is go to the school office, fill out forms, and have the records sent to the new school. No letter is needed.
absent without leave
just say you are not guilty
falilure to report on duty