There's an Intern that lives in New Jersey and his parents claim him on there taxes. But now he's working in D.C for the summer and is also Staying in Virginia for the summer. Which State should he pay taxes to New Jersey or Virginia?

Actually, he has to declare the earned income on BOTH the Virginia and New Jersey tax return.

He will PAY taxes to Virginia as the state in which he worked, but, after listing the income on his New Jersey return, he will claim a tax credit on the New Jersey return (for the state in which he LIVES as a full-year resident) for the Virginia taxes he paid.

The result of claiming that credit is that he will NOT pay taxes to two different states on the same income.