Form W-2: Box 12 code

Box 12 of Form W-2 shows a code followed by a value.  The code indicates the type of payment. This is a listing of the codes for that box.
A: Uncollected social security or RRTA tax on tips. Include this tax on Form 1040.

B: Uncollected Medicare tax on tips.  Include this tax on Form 1040.
C: Taxable cost of group-term life insurance over $50,000 (included in boxes 1, 3 (up to social security wage base) and 5)
D: Elective deferrals to a section 401(k) cash or deferred arrangement .
E: Elective deferrals under a section 403(b) salary reduction arrangement
F: Elective deferrals and employer contributions (including non elective deferrals) to a section 408(k)(6) salary reduction SEP
G: Elective deferrals and employer contributions to a section 457(b) deferred compensation plan
H: Elective deferrals under a section 501(c)(18)(D) tax exempt organization plan
J: Nontaxable sick pay

K: 20% excise tax on excess golden parachute payments
L: Substantiated employee business expense reimbursements
M: Uncollected social security or RRTA tax on taxable cost of group-term life insurance over $50,000
N: Uncollected Medicare tax on taxable cost of group-term life insurance over $50,000
P: Exclude-able moving expense reimbursements paid directly to employee
Q: Nontaxable combat pay
R: Employer contributions to an Archer MSA
S: Employee salary reduction contributions under a section 408(p) SIMPLE

T: Adoption benefits
V: Income from the exercise of non statutory stock options
W: Employer contributions to an employee's Health Savings Account
Y: Deferrals under a section 409A non qualified deferred compensation plan
Z: Income under a section 409A on a non qualified deferred compensation plan
AA: Designated Roth contributions to a section 401(k) plan
BB: Designated Roth contributions to a section 403(b) salary reduction agreement
DD: Cost of employer-sponsored health coverage
EE: Designated Roth contributions under a governmental section 457(b) plan.
Forms W-2 provide information to your employees, social security, the IRS, and state and local governments.
Employers must file Form W-2 for wages paid to each employee from whom:

• Income, social security, or Medicare tax was withheld or
• Income tax would have been withheld if the employee had claimed no more than one withholding allowance or had not claimed exemption from withholding on Form W-4, Employee's Withholding Allowance Certificate.

Also, every employer engaged in a trade or business who pays remuneration for services performed by an employee, including non-cash payments, must file a Form W-2 for each employee even if the employee is related to the employer.
Form W-2C is filed to correct a previous Form W-2 submission. File a Form W-3C whenever you file a Form W-2C with Social Security, even if you are only filing Form W-2C to correct an employee's name or Social Security number (SSN).