The Full Form of TNC is‍ Tentative Non-Confirmation.

Your employer may inform you that your E-Verify case received a U.S. Department of Homeland Security (DHS) and/or Social Security Administration (SSA) Tentative Nonconfirmation (TNC) case result. A DHS and/or SSA TNC means that the information your employer entered in E-Verify from your Form I-9, Employment Eligibility Verification, did not match records available to DHS and/or SSA. A DHS and/or SSA TNC case result does not necessarily mean that you are not authorized to work in the United States.

Your employer must notify you of a TNC result and complete the referral process as soon as possible within 10 federal government working days after E-Verify issued the TNC result. You must decide whether to contest (take action) or not contest (do not take action) to resolve the TNC within 10 federal government working days after E-Verify issues the TNC result. You must notify your employer of your decision by the 10th federal government working day after E-Verify issued the TNC result or your employer will close your case in E-Verify.