I e-filed a new client's return, and both Federal and California were accepted.

But she just received a 12C letter from the IRS, requesting that she send in pages 1 and 2 of her 1040, along with any supporting documents for income, withholding, and estimated payments.  Or check a box that says that she didn't file.

I've dealt with 12C letters for missing 8962's, but what is this all about?  She's on Medicare with no ACA.  Is this suspected identity theft?