Where do I enter my TSP contributions as a deduction on my NJ STATE tax return? We have no TSP withdrawals, so there is no TSP income to report.

All you have to do is enter the W-2 as it is reported.  You will get a deduction on your federal return.  TSP contributions are taxed in NJ.  Contributions to retirement plans [other than 401(k) plans] are included in New Jersey wages.  Your state wages (Box 16) on your W-2 should be higher than the amount reported in Box 1.  If they are not, you will need to make an adjustment on your NJ return.  If you need to make an adjustment, read on.  

When you go through the NJ state interview, look for a page that says ''Other wage Adjustments - W-2''.  If you need to adjust your NJ wages to include this amount, enter TSP on the description line and enter the amount of your contributions.

Since you did no withdrawals, there are no 1099-Rs to report, only the W-2.  

Thanks you, DawnC.  I was afraid of that.  

How does NJ get away with taxing you when you are putting it in AND taking it out??

Also: they say (nj gov) that they don't tax 401k's .... isn't TSP a 401k?