Form W-2 Box 12 Codes Reference
Code	Description
A	Uncollected social security or RRTA tax on tips
B	Uncollected Medicare tax on tips (but not Additional Medicare Tax)
C	Taxable cost of group-term life insurance over $50,000
D	Elective deferrals under a section 401(k) cash or deferred arrangement plan (including a SIMPLE 401(k) arrangement)
E	Elective deferrals under a section 403(b) salary reduction agreement
F	Elective deferrals under a section 408(k)(6) salary reduction SEP
G	Elective deferrals and employer contributions (including nonelective deferrals) to a section 457(b) deferred compensation plan
H	Elective deferrals to 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 (former employees only)
N	Uncollected Medicare tax on taxable cost of group-term life insurance over $50,000 (but not Additional Medicare Tax) (former employees only)
P	Excludable moving expense reimbursements paid directly to members of the Armed Forces
Q	Nontaxable combat pay  [Military Certification Required]
R	Employer contributions to an Archer MSA  [Out of Scope]
S	Employee salary reduction contributions under a section 408(p) SIMPLE plan
T	Adoption benefits  [Out of Scope]
V	Income from exercise of nonstatutory stock option(s)
W	Employer contributions (including employee contributions through a cafeteria plan) to an employee's health savings account (HSA)  [Advanced Certification Required]
Y	Deferrals under a section 409A nonqualified deferred compensation plan
Z	Income under a nonqualified deferred compensation plan that fails to satisfy section 409A
AA	Designated Roth contributions under a section 401(k) plan
BB	Designated Roth contributions under a section 403(b) plan
DD	Cost of employer-sponsored health coverage
EE	Designated Roth contributions under a governmental section 457(b) plan
FF	Permitted benefits under a qualified small employer health reimbursement arrangement   [Out of Scope if premium tax credits are involved]
GG	Income from qualified equity grants under section 83(i)
HH	Aggregate deferrals under section 83(i) elections as of the close of the calendar year