A modified block-style letter is one type of conventional business correspondence. 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.
The customary and most formal approach to a business letter is block style, in which all material is aligned to the left margin and paragraphs are not indented. Business letters in standard format also include a colon after the salutation and a comma after the closing, in contrast to open style, which omits punctuation in both of those places. Modified block-style letters are not only considered slightly less formal than the full-block style but can be easier to read visually as well, with material more evenly balanced horizontally across the page.
Modified block-style letters also differ from semi-block style, which aligns all text on the left margin but features indents on all paragraphs and double or triple spacing between them. Modified block-style letters also differ from modified semi-block style, which indents the author's address, date and closing but indents these items at a given spot on the page, not necessarily centered or flush right. When using letterhead stationery, the writer's name, company name and address do not need to be repeated. The letter can begin with the date, flush right or a little to the right of center.