See the instructions for Form 1040 Line 62 page 53 - https://www.irs.gov/pub/irs-pdf/i1040gi.pdf#page=53
8. Uncollected social security and
Medicare or RRTA tax on tips or
group-term life insurance. This tax
should be shown in box 12 of Form W-2
with codes A and B or M and N. Identify
as “UT.”