Below is the explanation of the Box 12 Codes on the W-2 tax form.
A - Any uncollected Social Security tax or RRTA tax on tips. You’ll include this amount in your total tax liability on your Form 1040.
B - Any uncollected Medicare tax on tips. You’ll include this amount in your total tax liability on Form 1040.
C - If you had group term life insurance through your workplace, the premiums for any value over $50,000 become taxable income to you and are included here.
D - Contributions to a 401k or SIMPLE 401k retirement plan.
E - Contributions to a 403b retirement plan.
F - Contributions to an SEP IRA retirement plan.
G - Contributions that you made and any employer contributions to a 457b retirement plan.
H - Contributions to a 501(c) tax-exempt plan.
J - Non-taxable sick pay.
K - Excise tax (equal to 20%) on excess “golden parachute” payments.
M - Uncollected Social Security tax or RRTA tax on the premium value of taxable group term life insurance over $50,000 for former employees.
N - Uncollected Medicare tax on the premium value of taxable group term life insurance over $50,000 for former employees.
P - Reimbursements for job relocation moving expenses paid directly to you, and not included in boxes 1, 3, or 5.
Q - Non-taxable combat pay. This isn’t subject to tax, but you can use it to calculate your Earned Income Credit if it will help.
R - Employer contributions to an Archer Medical Savings Account. These are not common anymore.
S - Employee contributions to a SIMPLE retirement plan.
T - Any adoption benefits paid to you by your employer. Use Form 8839 to calculate what portion may be taxable income.
V - Income from exercising non-statutory stock options.
W - Employer contributions to your health savings account (HSA). You will need to report this amount on Form 8889.
Y - Salary deferrals under your 409A non-qualified deferred compensation plan.
Z - Income received under 409A non-qualified deferred compensation plan.
AA - Designated Roth contributions to a 401k retirement plan.
BB - Designated Roth contributions to a 403b retirement plan.
DD – Cost of employer-sponsored healthcare (this amount is not taxable.)
EE – Designated Roth contributions to a governmental 457b retirement plan.