The difference between the two here is that one uses the honorific -시- and the other one doesn't. Both are right, but you can use the honorific to someone who is older than you or is in a higher position than you. So for example your boss. Also you use honorific to people you don't know. 갔어요? - I would still use this to someone who is older than me, but I'm closer with. 가셨어요? - here I'm using the honorific and I would say this to someone i don't know or an older person etc It varies from person to person when to use each one, but to be safe and not offend be polite and use it, until they say 편하게 할까요? shall we speak more comfortably, and you can be more casual with speak.

가셨습니까? is composed as 가(다) + 시 + 었 + 습니까 가다 : to go 시 : honorific suffix 었 : past tense suffix 습니까 : honorific interrogative suffix 갔습니까? is composed as 가(다) + 았 + 습니까 가다 : to go 았 : past tense suffix 습니까 : honorific interrogative suffix The difference is the suffix 시 It denotes that the subject of the action is older than the speaker. 습니까? denotes the listener is older than the speaker. 1. when the listener and the subject of the action are different. Are you sure that he/she leaved? you : the listener he/she : the subject of the action 가셨습니까? (Both listener and subject are older than the speaker.) 갔습니까?(listener is older than the speaker and subject is younger than the speaker) Here are some other forms. 가셨어요?(listener is older than or equal to the speaker and subject is older than the speaker) 갔어요?(listener is older than or equal to the speaker and subject is not older than the speaker) 가셨어?(listener is younger than or intimate to the speaker and subject is older than the speaker) 갔어?(listener is younger than or intimate to the speaker and subject is younger than the speaker) 2. when the listener and the subject of the action are same Did you go? 가셨습니까? (listener is older than the speaker.) 갔습니까?(X) Here are some other forms. 가셨어요?(listener is older than or equal to the speaker) 갔어요?(listener is younger than or equal to the speaker) 가셨어?(X) 갔어?(listener is younger than or intimate to the speaker)

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