Rejected Return from dependent's SSN "already in use"

[cloudwizard]

My ex-wife filed taxes before I did, and put down my son's information but opted out of claiming him as a dependent. I claimed him as a dependent, correct SSN and all other information, but my return is being rejected because his SSN is already on her return. Her return was accepted and paid out already. I had this issue last year, and got it resolved but it happened again this year. What am i doing wrong?

[xmasbaby0]

Your "ex" made the mistake if she entered the child's information but did not say that there is a signed agreement with the other parent.  She got all of the child-related credits if she did that.   If you are the one who can claim the child then you will now have to print, sign and mail your return.. You cannot e-file this year with the child's SSN on your return.   The IRS will sort out the duplicate use of the child's SSN.      Who does the child live with?

Are you the custodial parent?  Do you have an agreement with the other parent to allow the other parent to claim them--due to divorce or that you live apart and share custody?  Did one of you sign a Form 8332?

If there is a signed 8332 then the custodial parent retains the right to file as Head of Household, get earned income credit and the childcare credit.  The non-custodial parent gets the child tax credit for children under the age of 17.

As far as the IRS is concerned, the custodial parent is the one with whom the child spent the most nights during the tax year--at least 183 nights.