What is the base form for 되세요
Example Hello Formal:
이름이 어떻게 되세요 ?
Korean Language Stack Exchange is a question and answer site for linguists, teachers and students of the Korean language. It only takes a minute to sign up.Sign up to join this community
It is 되시다, which is an honorific form of 되다 (to become, to work out).
되시(다) + 어요 => 되시어요 => 되셔요 => 되세요.
시어 contracting to 셔 is a case of the common 이어->여 pattern, whereas 셔요 becoming 세요 only happens in this type of 시어요/셔요 case. The latter only happens when 시어요/셔요 comes after the verb stem, not in general, purely for phonetic reasons (세요 is easier to pronounce and sounds more natural than 셔요). 되시어요 and 되셔요 are also valid forms even though they are not as commonly used as 되세요.