How To Write A Letter To Boss About Coworker . In the heading of your employee complaint letter, you should clearly state why you’re writing the letter. 5.4 describe how your worker can be an asset to the company; how write farewell email colleague coworkers sample letter colleagues from www.pinterest.com Write care of: and then the supervisor's. Apology letter example for not attending a retirement party. If you boss is unable or unwilling to deal with it, contact your human resources department.