수고했습니다 수고하셨습니다 Both come from 수고하다 - to make an effort Both use the past tense particle 였 - 수고했다 - to have made an effort Both are conjugated formally with ((으)ㅂ니다/)습니다, which is used when the person you are talking TO deserves to be spoken to more respectfully or politely - 수고했습니다 The second one uses the honorific particle 시, which is used when the person you are talking ABOUT deserves more respect

I recommend looking here. Level 5 Lesson 2 / -시- (honorific) / -시-, 하시다 http://www.talktomeinkorean.com/lessons/level-5-lesson-2/ 감사합니다 :)