Formal letters should be written with proper english. When a formal letter is written it really should be written on letterhead. If there is not any letterhead just make sure you put who it is addressed to. You need to put the date on the top. You can go to the website www.letterwriting.com and it will help you write a formal letter. Make sure that when you write it you write good english
. and you do spell check. Never send a formal letter if you do not have the right spelling of words.