A formal letter is a type of letter that is written for professional purposes and follows certain guidelines and formats. It is usually written in a formal or professional language and adheres to conventional standards. Formal letters can be used in various scenarios that require communication with professional contacts or authorities, such as in the workplace, to communicate with heads of other companies, or to offer a contract or renegotiate the terms of an existing agreement.

The structure of a formal letter includes the senders address, date, receivers address, subject, salutation, body of the letter, complimentary closing, and finally, the senders signature. The overall style of the letter depends on the relationship between the parties concerned. Most formal letters start with "Dear," followed by the name of the recipient, and sometimes, this might be their title, followed by their surname.

Formal letters are sometimes useful because they produce a permanent written record and may be taken more seriously by the recipient than other forms of communication. They allow you to communicate with your colleagues, bosses, other companies, or those in authoritative positions like government representatives, and act as official modes of communication.

To write a proper formal letter, it is important to ensure that your words are professional, understandable, and well-received by the recipient. The following are some key elements of a formal letter and what to include in each section:

• Senders address
• Date
• Name/designation of addressee
• Address of the addressee
• Salutation
• Subject
• Body (Introduction, Content, Conclusion)
• Complimentary closing line
• Signature/name of the sender
• Designation of the sender

It is important to make sure that the intent and purpose of the letter are clearly defined, avoid making grammatical mistakes, and avoid using informal language in a formal letter.