Guidelines to Write an Apology Letter for Mistake at Work An apology letter means a forgiveness letter, which is written in the case of any mistake made by the person writing the letter. 5.2 Frequently Asked Questions about Apology Letter for Work Mistake What is an Apology Letter for a Mistake at Work?Īn apology letter for mistake at work is a letter written to the employer by an employee in the case of any mistake made by an employee at work.