If an employer could not collect all the social security and Medicare taxes, railroad retirement tax on tips or group term life insurance owed on tips, the uncollected taxes will be shown in box 12 of Form W-2 (codes A, B, M or N). Click here for a description of those codes.
There may be uncollected taxes if the taxpayer's regular pay was not enough for the employer to withhold all the taxes they owed and they did not give their employer enough money to pay the rest of the taxes. To report these uncollected taxes, the taxpayer must file a return even if they would not otherwise have to file. You must use Form 1040. (You cannot file Form 1040EZ or Form 1040A) The tax program will include the taxes in your total tax amount, and enter UT and the total of the uncollected taxes next to the line.