"Then 4 months later (September), I moved back to my original place in NJ."
Since you lived in NJ for 8 months of the tax year, by NJ's 183-day rule you are a full-year resident of NJ for tax purposes. ALL your income for the year, regardless of where you earned it, is taxable by NJ.
In addition, all the income you earned by working in NY is taxable by NY state. It is not taxable by NY city unless you became a resident of NYC. If you kept and maintained your home in NJ during your absence in NY, and then returned to it after only 4 months, then you may be able to file in NY as a non-resident - which would relieve you of having to pay NYC taxes. NYC is more likely to regard you as a non-resident if you kept your drivers license, voter registration, etc., in NJ while you were away in NY, in addition to keeping your home in NJ.
@Hal_Al -- comments?
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
