IRS amended my federal tax return with a CP-2000 to add some interest from a 1099-INT I had misplaced when filing fed return. I sent them extra payment they asked for (a few hundred dollars).

I live in NJ. Extra state taxes as a result of extra income would be around $200 or so, plus a little interest. Should I file an amended NJ return myself or wait for NJ to get the update from the IRS (I understand they have any information sharing with the IRS) and send me a notice for extra taxes ? It would be a bit of a pain to amend NJ return, and I am inclined to wait for them to bill me. There would be extra cost of interest till that time, but at 6% or so, its quite small. Professional costs of amending NJ return would likely be around $50 at least with a lot of paperwork. For such a small sum of taxes, is there any harm in just waiting for NJ to bill me ?

My experience with NJ is that it typically takes them about 3 years to catch up with filing errors. So 6% interest for 3 years on $200 owed will incerase the amount you'll eventually have to pay by about $36. I guess you need to decide whether you'd rather pay $200 now or $236 later.

If you do not amend a North Carolina return within 6 months of the change, there is a 5% per month penalty up to 25% of the tax. By the time NC bills you, you would owe the tax, interest, and another 25%. You may want to be sure New Jersey does not have anything like that.

Both MLSNC and ebaines make strong arguments for amending the return immediately.