Turbo Tax calculated a tax due amount on income that I earned in PA. However I am a NJ resident. I have already filed the return as a non-resident and scheduled the payment for April 14. I realize now that this may be an error. Should I file an amended non-resident return?
Yes, you should file an amended PA return. As you state in your question, as a NJ resident, your state has a reciprocal agreement with PA. Thus, if PA withheld taxes, then you file a nonresident reciprocal return to get those taxes back. Hopefully, you have not paid the amount "due" PA because you don't owe them anything. Even if you didn't have tax taken out, filing the reciprocal return as an amended return will cancel out what was originally sent.
Having said this, if your PA return was not sent, and no PA tax was taken from your check, you were not required to file with PA and can delete the return in TurboTax. In the Personal Info tab, you will answer no to the question if you worked outside of NJ, because of the reciprocal agreement. You are not considered to work in PA because you are not taxed there.
Yes, you should file an amended PA return. As you state in your question, as a NJ resident, your state has a reciprocal agreement with PA. Thus, if PA withheld taxes, then you file a nonresident reciprocal return to get those taxes back. Hopefully, you have not paid the amount "due" PA because you don't owe them anything. Even if you didn't have tax taken out, filing the reciprocal return as an amended return will cancel out what was originally sent.
Having said this, if your PA return was not sent, and no PA tax was taken from your check, you were not required to file with PA and can delete the return in TurboTax. In the Personal Info tab, you will answer no to the question if you worked outside of NJ, because of the reciprocal agreement. You are not considered to work in PA because you are not taxed there.
Unfortunately, the PA return was transmitted. The payment is scheduled for April 14 as a withdrawal from my checking account. If I file an amended PA return via Turbo Tax prior to the scheduled payment date, will the scheduled payment be cancelled or will it be withdrawn and later refunded?
I suggest contacting PA tax authority. They may be able to cancel the payment. Here's a link to their website (copy and paste if there is no hyperlink): <a rel="nofollow" target="_blank" href="http://www.revenue.pa.gov/">http://www.revenue.pa.gov/</a>