Business Letter Format Modified Block. If you are using company letterhead, you will need to account for that in figuring the margin where the letterhead is placed on the page. Block format is the most common format for a professional business letter.it’s the easiest format to use and simplest to set up in your word processing program.
The image above shows a typical business letter using the block format. It differs from block format in that a modified block letter has the writer's name, company name, address, date and closing aligned a few spaces to the right of center or on the right margin rather along the left margin. Your address (or the address of the company you represent).
If you are corresponding with someone you already have a good working relationship with, the modified block style letter is a good one to use.
Nowadays, this style is appropriate in most contexts. For example, return addresses can be centered or begin at the left margin or begin at the horizontal center of the page. Also sometimes referred to as indented block format, this style is the same as the modified block format except that each paragraph is indented. The style and format for writing business letters has evolved over the past several decades and has adjusted itself to more or less the corporate culture of its times.