Are state income taxes based on the address of the employer or the employee?

I worked in New York over the summer, but I'm a California resident, and I used my California address for all the paperwork, so that's the address listed on my W-2 (and also where all my paychecks were sent). I have to file tax returns for both states either way, but I'm not sure whether to list my summer pay as NY or CA income. Is what state my income was earned in determined by my employer's address, or by my address as listed on my W-2? If it's considered NY income, then do I file my CA tax return as a part-year resident, or will I have to CA tax on it as well?

Public Comments

1. You have to file a tax form in the state that you work in, as well as the state that you live in. In this case, you are a California resident, and a New York non resident. The states will make you figure out your taxes as if you earned the entire income in that state, then you take the ratio of earnings and multiply it by the tax. If you earned 1000 dollars in NY and 9000 in CA, then your total income is 10000. The CA tax on 10000 is lets say $100, so $9000/$10000 = 0.9, so therefore 0.9 * $100 = $90. The same goes for NY, more or less.
2. State income taxes are based on the employee's state of residence. If you have taxes withheld for one state and you are a resident of another state, you will have to file your resident return and non resident return.
3. pisceswise is correct, but not complete. You will file a NY Non Resident return for your New York income only. You will file a CA Resident Return for all income including the income earned in NY. CA should give you a credit for taxes paid to NY. If CA's tax rate is higher than NY, your credit should be the total amount of tax paid to NY. If CA is lower, then your credit will be limited to the tax that CA would have assessed on that income.