It's a little difficult to explain... you can see 동사+오다 in informal/conversational situation. There's not a big difference between 주소를 쓰세요/김밥을 사면 될 거예요 and 주소를 써 오세요/김밥을 사 오면 될거예요 but just a nuance. 여기에 이름과 주소를 쓰세요= Please write your name and address down here 여기에 이름과 주소를 써 오세요=Please write your name and address down here (and "bring it back to me.") 김밥을 사면 돼요. 될 거예요. you can buy 김밥/ It will be okay if you buy 김밥 김밥을 사오면 돼요. 될 거예요. you can buy (and bring) 김밥 / It will be okay if you buy 김밥 (and bring it.) There are many usage of 오다 but actually, the usage you asked is grammatically not right.. even though many Korean uses that expression a lot in their daily life^^; I'm not a teacher or something, I just hope this will help you a little. Have a nice day~