A minimum of 10 to 12 parts is essential for a good business letter. Parts of Business Letter. 30 Professional Business Letter Templates Word Informal Business Letter -Informal Business Letter is used for casual correspondence but doesntnecessarily has to have a casual tone of language. What essential parts of a business letter . Business Letter Structure. What was interesting is that you mentioned Block format which I agree with since its easier on the eyes but I use Arial 12 as a font size. Professional types of correspondence such as letters of application sales letters and letters of reference differ from friendly letters in that they must follow a specific format and should never include informal or slang language. Parts of a Business Letter 1. Sender addressee return address inside address salutation complementary closing as well as spacing. The outer quality of a business letter means the quality of its outer appearance. The heading is the return address of...