 All you have to do is check a box and sign your name. No documentation required. It's on the honor system. You can register to vote, including in federal elections. Now, a few years ago, the Supreme Court of the United States, a bad ruling in my view, with a great dissent by my former boss, Justice Alito, the rest of the Supreme Court concluded that the National Voter Registration Act actually prohibits the states from asking for proof of citizenship when you fill those out.