I just got my returns rejected due to my children's SSN already being filed under my exes return in connection with child care expenses. Do I need to mail in my returns?

[PaulC1]

If you want to claim your children as your Dependents, yes, you will need to mail in the return and then the IRS will contact you and your ex to decide who has the right to claim the dependents. If you and your ex have an agreement that your ex is going to be the one to claim the Dependents, then you should be able to e-file after you indicate that the children are being claimed by your ex.

[retiree]

If someone else (incorrectly) used the SSN’s you cannot e-file.  Your only option is to PRINT and MAIL your return, and let the IRS sort out the issued.  They will contact you and the other party and determine who is entitled to file.

When mailing your return it is best to go to the Post Office and send it Certified with Return Receipt.