Business letters are generally formatted using block style formatting. There are three basic types of block style: standard block style, modified block style and semi-block style. Newer letter styles, such as the simplified style, are based on the block style. Each style prescribes margin widths, alignment, paragraph spacing and the order of the letter’s content.
TL;DR (Too Long; Didn't Read)
If you’re writing a block style letter, begin every new line at the left margin with no tabs or indentations.
Block Style Definition and Preferences
Letters written in block style have every line aligned at the left margin. This makes them easy to read and quickly. The standard block letter style and its variations are meant to be used as guides to help you format letters. Examples of each style and free templates are available online, each a bit different than the next.
Some companies require their employees to use a specific, management-approved format. If this is the case with your company, they’ll provide you with a business letter template to ensure that their preferences are followed. However, because each line in a standard block style letter is flush with the left margin, it is very easy to follow its guidelines without a template.
How to Format Block Style
Your name and address, single spaced, is the first component of a letter written using standard block style. However, if you’re using letterhead you can just skip to the date, which comes after name and address. The date is followed a few lines later by the name and address of the recipient which is also single spaced. One line later, the salutation begins the letter.
In the body of the letter, each single-spaced paragraph is separated by one blank line. Similarly, one blank line separates the final paragraph from the closing ("Sincerely yours" or "Thank you," for example), which is followed a few lines later by the signature block. As mentioned above, each line is flush with the left margin.
The signature block consists of space for your signature, usually three or four blank lines. This space is followed by your name typed out. So you’ll sign between the closing and your printed name.
Variations on Block Style Letters
Each component of a standard block style letter is included in the modified block style. The difference is that the date, the closing and the signature block begin in the center of the page. Note that they are not centered on the page but are center-justified.
A semi-block style also follows the modified block style. However, instead of making each paragraph of the letter’s body flush to the left margin, the first sentence of each paragraph is indented (no more than 10 spaces).
Whichever style you choose stick to it for the entire letter. Mixing up styles will make your letter look unprofessional. It’s appearance will distract the reader from its content. This is especially important when you’re writing a cover letter for a job.
Block Style is Evolving
The standard block letter style continues to be modified. For example, the Administrative Management Society created the simplified letter style. It is based heavily on the standard block style: each component begins at the left margin and follows similar spacing guidelines. However, the style omits two components (the salutation and the closing) and adds a component (a subject line).
Much like that used in a memo or e-mail, the subject line is typed in all caps two blank lines below the recipient’s address and two lines before the first paragraph. By omitting the salutation and closing, the writer avoids the common problems of inappropriate salutations and awkward courtesy closings.