"환급체크가 2장 오자나요.. (주정부에서 하나오고 연방정부(맞나요?)에서 하나오고...) 주정부 체크나 연방정부(?) 체크에 뒤에 다 싸인을 하고 디파짓을 해야하는게 맞나요?"---->Yes. You need to endorse your tax refund check from the IRS/State. Just sign your name above the line, and it's good to write "for deposit only" underneath it.There is a bunch of wording on the back and then a line but it doesn't say anything about endorsing. Endorsing a check means to sign the back of it in order to cash it, deposit it or sign it over to someone else.