Final answer:
The standard top margin for formatting a block style business letter is 1 inch. Everything should be left-justified and in a legible font such as size 12 Times New Roman or Arial.
Step-by-step explanation:
When formatting a block style business letter, the standard top margin should be set to 1 inch, as this is the usual margin setting for 8 1/2 x 11" standard printer paper when creating professional documents. It's important to use a legible font such as size 12 Times New Roman or Arial for the body of the letter. All parts of the letter, including your return address, the date, the inside address, greeting, body, and closing, should be left-justified, with no indentation at the beginning of paragraphs, and with single spacing within paragraphs and double spacing between them.