Despite informal correspondence styles changing rapidly with email and social networking sites, the style and format of formal letters has remained somewhat constant. While informal letter styles can be used in a broad range of situations, they are not suitable in situations when you want to make your letter seem official or professional.

Purpose

While informal letters are not usually sent for official matters such as complaints, inquiries and requests, formal letters usually are. This affects the tone and information displayed in the letter. The purpose of the letter must be clear, and the information required to take responsive action must be available.

Recipient

When writing an informal letter, the recipient of the letter is often known to you. If you are sending a formal letter to a person or company, you usually will not be familiar with the recipient. In this case, the quality of the content is entirely responsible for getting your message across and making a good impression on the reader.

Structure

There are several parts to the structure of formal letters. Informal letters have little structure other than a greeting, a main body and a conclusion. A formal letter has the address of the person you are writing to at the top left side of the page with a suitable greeting one line underneath. Write your own address on the top right of the page with the date underneath. Sign your name under a suitable conclusion, which follows the main body of the letter. Finally, print your name below your signature.

Greeting and Complimentary Close

You can greet the recipient of an informal letter in any way that you feel is appropriate. When you write a greeting in a formal letter, it must follow salutation rules. Use "Dear Sirs," for unknown recipients. If you know the recipient's name, use "Dear Mr./Ms./Mrs. ...." . When using the greeting "Dear Sirs," you must close your letter "Yours faithfully," whereas "Yours sincerely," should be used if you have written the name of the recipient.

Content

It is good practice to split the main body of a formal letter into three parts. Begin with an introductory paragraph that concisely describes the purpose of the letter. Following this, the main body describes the points that you want to make in your letter and can be formed of more than one paragraph. Finally, your concluding paragraph describes the action you wish to be taken by the recipient, such as refunding your money or contacting you regarding a job position.