In case of working one week in each state, look at the instructions of 1040 form for each state. Unless you are filing as Nonresident tax alien in all states, you must file as resident in one of the states. To find out whether you need to file in other states or not, look at the threshold income level in each state. If your paycheck comes from the same parent company for all those states you worked for (such as a single W2 form at the end of the year), I guess, you don't need to file separately in multiple states.