How To Write A Business Style Thank You Letter . In all these years apart from being a business partner, you have also become a friend and family. Although this is a thank you letter, it should still use the typical formalities that are in other business letters. FREE 6+ Sample Business Thank You Letter Templates in PDF MS Word from www.sampletemplates.com In the subsequent sections, provide details on the subject to make a solid case. In the last paragraph, reiterate the reason you are writing the letter. [sentence about why the person’s contribution deserves your gratitude.] [sentence explaining the positive effect the recipient’s contribution had.] [optional: