The IRS doesn’t actually know - it trusts you to report your status accurately. Of course, they could demand proof during an audit, I suppose, but “proof” can g

The IRS doesn’t actually know - it trusts you to report your status accurately. Of course, they could demand proof during an audit, I suppose, but “proof” can get fuzzy. But on top of that, not everyone, not even every adult, is required to file taxes. People can and do live their whole lives never filing taxes. So, “this person has never filed a return” is not proof of anything. It also doesn’t share this information anyway - US agencies are not big on sharing and in the case of the IRS, there’s privacy reasons. But of course, if you tell the IRS you’re a citizen and you file taxes ten years in a row, they might have questions if you suddenly stop. :) Here are the voter registration requirements in New Hampshire, to pick a state out at random, for example: https://sos.nh.gov/media/nbhlz4bt/registering-to-vote-in-new-hampshire-oct2021.pdf https://sos.nh.gov/media/nbhlz4bt/registering-to-vote-in-new... You can literal simply pinky swear and sign a document in front of an election official at your voting place and time that you are an eligible voter to register, and then go vote. They have no practical way of truly verifying what you say in most cases. There are legitimate edge cases that need this, so that’s why things work this way.