Where do you file taxes if you work in multiple states?

You file in your state of residence The above is true, but not complete. You always file in your state of residence, and all "intangible" type income (like interest on bank accounts), is considered earned there. Earnings from employment, whether paid as a W-2 or 1099, or on a 1065 as a partner, get taxed where earned. You file everywhere you worked, even for the shortest period of time. Most states will even consider one day of work there, or attending more than a specified number (generally 5 days) at a seminar there, as earning income there. How it works, allocating your earnings away from your state of residence, or specifically marking the situs of the earnings, and taking either a credit for taxes paid other place or removing the income claimed by other places, varies from state to state and circustances.