@brianbeutler
YOU do the assigning ... when you enter the W2 it asks who the form is for. And later there was a warning screen where you could have made the correction before you filed ... so sadly this is a user data entry error. Check your 2017 return to make sure you didn't make the same mistake again especially if you transferred in the prior year info ... if you did then amend the return before the IRS catches the error.
