There is no way for me to know which of your dependents where already claimed on someone else's tax return and the IRS would not tell you if you asked them. Do you know of someone else that could have possibly claimed your children, like an ex-spouse? If not, there is a lot of identity theft occurring these days and fraudulent tax returns using other people's social security numbers are being filed in record number. Since your tax return has been rejected by the IRS, the only option you have is to paper-file your tax return. To do this, you would select Paper-File instead of Efile when you are in the File section after completing your return. Then print, sign, date and mail your tax return by April 18, 2017. You may also consider contacting the IRS at 1 (800) 829-1040 but they will most likely give you the same advice.