I've never filed any tax before in USA until I have to file 2017 tax, for which I requested extension on Apr 17, 2018.
I moved to NC in 2015 and I guess the clue NC knows I live there is that I have a NC driver license and car registered in NC. I did not file any tax to NC and IRS before. I did not apply for business license from both states.
I started selling on eBay in NC from beginning of 2017. In the middle of 2017 my lease ended and I moved from NC to PA. For some reasons I have not changed car registration nor exchanged driver license. They are still valid in NC now.
As for the preparation for state tax filing, I find it difficult to figure out how much exactly I earned in NC and PA respectively. The income earned in NC would be estimated to be close to 20% of whole income.
I am a self-employment person with no W2. I have to file 1040 schedule C. eBay sales are my ONLY income. I got 1099K from PayPal early this year which shows ONLY my PA address (NO previous NC address). Yes, I changed my PayPal registration address from NC to PA when I moved. I wonder other than IRS if PayPal also sends 1099k to local state tax authority? If yes, it sends to PA only or both PA and NC?
For convenience, what if I only file tax with state PA for the whole income and ignore NC? Will NC go after me once I finish filing to IRS?
If you accepted electronic payments for your Ebay sales, the state may have received the information that way.