You will not report this on your tax return. The W-2 reconciliation is a communication from the Social Security Administration (SSA) that the wage data processed by the SSA was less than the amount reported to the IRS. Because the wage data is different, the SSA assumes that the processed earnings are incorrect. The Social Security Administration sends a notice and a questionnaire to the employer asking them to resolve the differences.
More information can be found here: http://www.ssa.gov/employer/recon/recon.htm
