Differences between business letters and the less formal format and style of friendly or personal letters can be found in the structure of a proper business letter. Personal, friendly letters allow a writer discretion as to the layout and other ingredients. Business letters should follow strict guidelines for style and form. Key elements such as layout, paragraph structure and technical formatting differentiate a proper business letter from a less formal personal letter.

Heading and Closing

The heading of a business letter should include the writer's name and address, and the date. Justify the heading to the left margin and single space the information. The recipient's contact information should be separated from the sender's heading by a single space and include the recipient's full name and address, including zip code. A writer constructing a friendly letter can choose to use only a salutation at the heading of the letter. The closing of a business letter requires a closing greeting and a signature. Oftentimes a business letter will include the signature as well as the author's name typed below and any credentials or titles held by the writer. Use four spaces between the closing greeting and the typed name for the handwritten signature. The name of the sender and a less formal greeting suffices when closing a personal letter.

Style of Body

Personal letters of a friendly nature can be crafted without the stylistic constraints of a proper business letter. The sender can choose a style or tone to match the normal characteristics of interaction with the recipient. In a business letter, the style should in keeping with the intent of the letter. Business letters meant to acquaint the recipient with the sender or business services should start with an introduction. The sender should then use the balance of the text to inform the recipient of the intent of the letter or the request for action. For example, a sales letter should introduce the seller and the product, address how the product will serve the recipient, and end by calling the reader to action -- buying the service or product.

Technical Differences in Format

Standard technical norms for business letters include 1-inch margins at the sides with a 1.5-inch space at the top and bottom margins of the page. Dates in business letters should be spelled out, not abbreviated, and include the month, day and year. Writers should use appropriate titles in business letters but avoid redundancy: Dr. or MD, not both. The recipient's full name should appear in the salutation, with a colon in a business letter. A personal letter can include a first name or title and last name followed by a comma. There should be one space between the heading, the writer's contact information and the opening salutation. One space is also standard between the salutation and each of the paragraphs in the body of the letter. Use 12 point serif fonts such as Times New Roman in a business letter and single line spacing throughout. Business letters should always be typed, but handwriting friendly letters adds a personal touch.

Important Post Scripts

Following the closing, business letters should contain appropriate postscript information such as disclosure of copies. A "cc:" signifies that the letter was also forwarded to additional parties. The postscript is also the proper location for notation of enclosed material in a business letter. Accompanying documents should be referenced as included items after the closing signature, with the number and nature of the enclosures standard in a business letter.