"안녕히 계세요" and "안녕히 계십시오", both are basically same, but the latter is more polite; the former is more casual/plain. "안녕히 가세요/가십시오" these are used when someone leaves from you, for example, your customer leaves from your store. Thus, those are can be used at the same time by their positions. Customer: Okey. Here is my credit card. Clerk: Wait a second... All right. It's done. Customer: 감사합니다. 안녕히 계세요. Clerk: 네. 안녕히 가세요. As you can see, in this situation, the customer can say "안녕히 계세요," then the clerk would say "안녕히 가세요." In daily routine, "-세요" forms are usually used, if the situation is more formal, it is likely that "-십시오" forms are used. Hope it helps. :)

안녕히 가십시오. 안녕히 가세요. is when leave someone from your area. 안녕히 계십시오. 안녕히 계세요 is when you leave somewhere say goodbye 안녕히 가십시오 and 안녕히 계십시요 This can use more business relationship 안녕히가세요. And 안녕히계세요 This can use anytime.