Most states tax all income earned in their state, regardless of your residency.
The general rule is that some States will require you to claim the gambling winnings in the state where they were won. For example, if you win $620 from a horse race but it cost you $20 to bet, your taxable winnings are $620, not $600 after subtracting your $20 wager. The second rule is that you can't subtract the cost of gambling from your winnings. For example, if you hit the trifecta on Derby Day, you must report the winnings as income. The first rule is that you must report all winnings, whether the place that you gambled reports them to the government or not.
