How to Format a US Business Letter
The main formats for business letters in the US are called full block format and modified block format.
* Full block format means that all the elements of the letter are left-justified so that the start of each line is at the left-hand margin. This is the more formal style, so use it if you’re unsure which to go for.
* Modified block format means that some elements of the letter are shifted over to the right. Nowadays, this style is appropriate in most contexts.
How to Format a US Business Letter