W-2 Box 12 Codes Explained: What Every Letter Means on Your Tax Form

What Is Box 12 on a W-2?

Box 12 on your W-2 form contains coded information about various types of compensation and benefits your employer provided. There are up to four Box 12 entries (12a, 12b, 12c, 12d), each with a letter code followed by a dollar amount.

Complete List of W-2 Box 12 Codes

Health & Insurance Codes

• Code DD: Cost of employer-sponsored health coverage. This is informational only — it does NOT affect your taxable income. It's the combined employer + employee cost.
• Code W: Employer contributions to a Health Savings Account (HSA). This amount is excluded from your income.
• Code FF: Permitted benefits under a qualified small employer health reimbursement arrangement (QSEHRA).

Retirement Codes

• Code D: Elective deferrals to a 401(k) plan. Reduces your taxable income.
• Code E: Elective deferrals to a 403(b) plan. Reduces your taxable income.
• Code F: Elective deferrals to a 408(k)(6) SEP. For self-employed or small business.
• Code G: Elective deferrals to a 457(b) plan (government employees). Reduces taxable income.
• Code H: Elective deferrals to a 501(c)(18)(D) tax-exempt organization plan.
• Code AA: Designated Roth contributions to a 401(k). Already in your taxable income — tracked for basis.
• Code BB: Designated Roth contributions to a 403(b). Same as AA but for 403(b).
• Code EE: Designated Roth contributions to a governmental 457(b).
• Code S: Employee salary reduction contributions to a SIMPLE IRA plan. Reduces taxable income.

Life Insurance & Other Benefits

• Code C: Taxable cost of group-term life insurance over $50,000. Added to your taxable wages.
• Code J: Nontaxable sick pay (typically short-term disability). Informational.
• Code K: 20% excise tax on golden parachute payments. Rare, affects highly compensated executives.
• Code L: Substantiated employee business expense reimbursements (nontaxable). Informational only.

Transportation & Housing

• Code P: Excludable moving expense reimbursements paid directly to employee (military only, as of 2018 tax reform).
• Code Q: Nontaxable combat pay for military members. Election option for EITC purposes.

Stock & Deferred Compensation

• Code V: Income from nonstatutory stock options. Already included in Box 1 wages — informational.
• Code Z: Income under a nonqualified deferred compensation plan that fails to meet Section 409A requirements. Subject to additional 20% tax.
• Code Y: Deferrals under a Section 409A nonqualified deferred compensation plan. Not currently taxable.

Other Codes

• Code M: Uncollected Social Security tax on the taxable cost of group-term life insurance over $50,000 for former employees.
• Code N: Uncollected Medicare tax on same.
• Code R: Employer contributions to a Medical Savings Account (Archer MSA). Excluded from income.
• Code T: Adoption assistance provided by the employer. May be excludable up to annual limit.
• Code U: Section 409A deferrals. Informational.

The Most Common Box 12 Codes

For most employees, you'll only see a handful of these codes:

1. Code DD (health insurance) — appears on nearly every W-2, no tax action needed
2. Code D (401k contributions) — reduces your taxable income
3. Code AA or Code EE (Roth contributions) — no reduction but tracked for basis
4. Code W (HSA contributions) — already excluded from income

Do I Need to Enter Box 12 on My Tax Return?

Most Box 12 codes are informational and don't require separate entry on your Form 1040. The codes that DO require action:

• Code W: Enter HSA employer contributions on Form 8889
• Code C: Taxable life insurance — already in Box 1, but verify
• Code Z: Additional 20% tax — requires Form 1040, Schedule 2

If you're using tax software (TurboTax, H&R Block, etc.), simply enter the code and amount as shown on your W-2 — the software handles the rest automatically.