Both. You will need to report this sale of NY property on both a NY nonresident state income tax return and on your NJ resident state income tax return.
You
will need to file as non-resident for NY (for your NY source income only - your
NY capital gains for property located in NY). You will also need to file a NJ resident state tax return (for all
income from all sources including NY capital gains). You will get a state tax credit in
NJ for any NY state taxes that you paid on your nonresident NY state tax
return.
You
will want to work on your non-resident NY state tax return first. You will then
take a tax credit from your non-resident NY taxes on your resident NJ state tax
return. (Please note that you will only get a tax credit for your NY taxes up
to the amount of NJ taxes that would have been paid if the income was earned in
NJ).
Just
follow the TurboTax guide when working on your states (remembering to do your
non-resident state return first) and TurboTax will do all the calculations and
credits to your resident states return
Here
is additional information about filing in multiple states (select "see
more answer" to view the entire attachment)
https://ttlc.intuit.com/replies/3300797
