The most formal way of ending a letter is ‘Yours faithfully’ (when you don’t know the name of the person you are writing to). When you do know the name of the person (and it is a formal letter) you sign off ‘Sincerely’ or ‘Respectfully yours’. ‘Best regards’ and ‘Kind regards’ are less formal (they’re not used to end very formal letters). If the letter is to a friend, it really depends on you and on how close the friendship is between you and your friend. You could sign off ‘Your friend’, ‘Take care’, ‘Wishing you the best’, ‘Be well’, ‘Cheers’ or ‘Take it easy’. If you want to be fun and creative, you can say ‘Over and out’, ‘Peace, love and unity’ or even ‘Tag! You’re it’. =)

Sincerely is more formal

i think both of them are foemal, u can use them

i would say "sincerely" is more formal but there is very little difference. no one will be offended with either ending. Both are polite, and is is hard to say which is more polite than the other. i see "best regards" used a lot in business because it is formal is more detached. I would probably use "sincerely" to someone i am or want to be close to, like a letter to an author i look up to because it is not do detached. sorry if i confused you!

both are formal and can be use in a letter. cowboy..