The short answers: Yes, you can amend *just* the state return. No, you can't e-file it.
I faced this situation a year ago to correct an under-reported withholding amount for a state return filed four years earlier, which was brought to my attention by the state (CA) via a letter. As in your case, my federal return for that year was *not* affected. As I recall, I had to use the TurboTax version for that year, which was still loaded on my PC and navigate to the section for amending returns. (If you don't use the online version of T-Tax, my advice is to keep those older versions loaded on your machine for as long as the IRS or state taxing agency can look back. I don't know how that works w/ the online version.) Since only the reported withholding was affected, this took all of ten minutes to do. TurboTax, you do rock! Per the filing instructions, which I have in front of me, I was not allowed to e-file but had to print and *snail-mail* the amended return, along with a *copy* of the federal return for that year and the revised documents supporting the change. To my surprise, I had my refund, a mailed check, plu$ intere$t, back in less than three weeks. Though, it did happen to be late February, when I submitted the amended return. It seems e-filing is allowed solely for the current year's business. So, my friend, have faith, and roll up your sleeves. Good luck!
