A modified block business letter is a design format commonly used in business correspondence. As opposed to the full block format that aligns all parts of the letter at the left margin, the modified block format places the heading, date, complimentary close, signature and identification lines approximately halfway across the page. Each of these parts is aligned vertically. In addition, the paragraphs of a modified block letter are indented.
Use of the modified block format versus the full block format depends upon preference. Though the arrangement is different, the parts of the modified block business letter are the same as the parts of the full block business letter. Each letter begins with the heading, which contains the sender's address and the date. Following the heading is the receiver's address. The salutation is used to greet the receiver, immediately preceding the body of the letter. The complimentary close, signature and identification lines follow the body of the letter, with any enclosure or attachment notations placed at the end of the document. Spacing between these parts is identical in each of the letter formats.
In addition to full block and modified block business letters, another layout called the alternate block format exists. The alternate block format is identical to the full block layout, with the addition of a subject line.