Yes, most people only file in one state, but many may have real estate holdings in multiple states that generate income requiring multiple state returns, especially people in military who have lived and bought property in multiple states. My son's friend, age 27, now has rentals in two states, and if his wife gets assigned to another state, they will buy property there. My youngest, just entering the army as an officer, is already planning on buying wherever he is stationed, easily could be more than 3 taxable states.
I have income property in 3 states besides NY, but fortunately one is TX, so no tax there.
Professional athletes, like baseball players, basketball, etc., get taxed in many of the states they play in for the income earned while playing there. How many states could that be??
