Final answer:
When not using a company letterhead, standard margins for a business letter are usually 1 inch on all sides for a professional appearance. Always verify for any recipient or industry-specific guidelines.
Step-by-step explanation:
If you do not use your company letterhead paper, the standard margins for a business letter are typically 1 inch on all sides. This means you should set the top, bottom, left, and right margins of your document to 1 inch. Proper margin settings ensure that the letter is neatly formatted and professional in appearance, which is crucial for business correspondence. However, it's always good to check if there are any specific guidelines provided by your company or the recipient since some industries or organizations might have their own preferences.