Business-related and semi-formal letters may close with ' Best regards ' (and notice that only the first word is capitalized) if the recipient is a reasonably familiar acquaintance; otherwise, use 'Sincerely yours'. 'With regards' and 'Regards' are short forms of 'Best regards' and are considered rather lazy substitutes.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.