Problem: The IRS - not eFile.com - rejected your Federal Income Tax Return because your dependent's SSN was already used on another Tax Return as a Primary Taxpayer or Spouse and that return has been accepted. Only one return with the same SSN can be accepted by the IRS per tax year.
Solution: Sign into your eFile.com account, click Federal Taxes/Review on the left side menu in your account, click the "I'd like to see all federal forms" link, click the Child or Other Dependent screen, correct the SSN on that screen, and click the green "Save" button at the bottom to save your changes.
If the SSN is correct, please PRINT your return from your account, sign it, and MAIL it to the IRS. See printing and mailing instructions plus addresses based on your resident state. You may need to print, sign, and mail your State Tax Return to the State Tax Agency. Then, contact the IRS at 1-800-829-1040 and discuss your tax return in more detail.
Contact us with questions: https://www.efile.com/tax-service/contact/efile-contact/