The phrase "dismissal letter" refers to a written document that officially ends someone's employment or job. It is a formal letter that informs an employee that they are being fired or let go by their employer. Full definition
Strangely, they were called one after the other on Friday, December 8, 2017, and handed dismissal letters. (ghanapoliticsonline.com)
Additionally, Giuliani's assertion that Trump simply wanted Comey to publicly say he wasn't a target in the Russia probe adds new weight to Trump's dismissal letter to the FBI director. (businessinsider.com)
He was served with his dismissal letter on Monday 15 May and asked to vacate post in two hours. (ghanapoliticsonline.com)