If you have verified the SSNs for all your dependents with the Social Security Administration and no one else is authorized to claim them, the following scenario probably applies to you:

• The SSN in question also appears as the filer, spouse, or dependent on another tax return for this same year.
• Whether the cause of this rejection is the result of a typo on another return or an attempt by another party to claim a benefit using your dependent's SSN, the IRS has security measures in place to ensure the accuracy of returns submitted.
• The IRS will, in some cases, contact taxpayers using the same SSN to claim a benefit and ask them to reconsider their eligibility or to provide supporting documentation.
• If you've verified this dependent's SSN and found no errors, unfortunately you need to file a paper return.
• Don't attach any information or documents with your return proving your eligibility to claim a dependent; if needed, the IRS will contact you by mail for any supporting documentation.