Thanks, everyone, for your concern and suggestions. The letter does not ask for ANY information about us, and it doesn't contain any information except our names and address. It also outlines immediate steps for us to take: Contact the IRS and gives the web link; contact local law enforcement to file a criminal complaint; obtain additional information via the state attorney general's website about contacting credit bureaus, banks, and other creditors. It asks that when we file our taxes, we do so via a hard copy/paper return. It also lists the phone number I called yesterday, which is the same number on the State website for the same division. When I called the number, the electronic answering service gave me a menu from which to choose. I punched in the number and told the person who answered that I had received a letter about possibly being the victim of identity theft. He said "I'll connect you to the office that handles that." The man I finally talked to never asked for anything more than my name, and then he asked "and DH's name is your spouse?" That was it for actual information exchange- he didn't ask for me to confirm anything else (address, birthdate, SS#,etc.). He answered some specific questions from me (but I gave him NO information about us at all). He also was pretty clear that this return was pulled because it's the first time our SS#s have ever submitted an electronic return; he says that's something the fraud division looks for as an indicator of possible identity theft.
I don't think this letter is a scam, but regardless, I'll keep the fraud alert active through the credit agencies and I'll also monitor the credit cards closely. I am going to talk with our banker today (she was out of town yesterday) to see what she recommends about the accounts. I'd rather be safe than sorry, even if it is a hassle.