12a — Box 12 Codes Updated for tax year 2025

What this line means

Box 12 reports specific types of compensation or benefits using single-letter or double-letter codes. Each entry has a code and a dollar amount. Up to four entries can appear across Boxes 12a through 12d. These amounts are not additional income beyond Box 1 — most are informational breakouts of amounts already included in (or deliberately excluded from) Box 1. The code tells you what category the amount belongs to.

Does this apply to you?

• You contributed to a 401(k), 403(b), or 457(b) retirement plan through payroll (codes D, E, G)
• Your employer provided group-term life insurance coverage over $50,000 (code C)
• You contributed to an HSA through payroll deductions (code W)
• Your employer reported the cost of your health coverage under the ACA (code DD)
• You had any other coded benefits — Roth 401(k) contributions (code AA), adoption benefits (code T), or others

Easy to overlook

Code DD is informational only — it is not taxable Code DD shows the total cost of your employer-sponsored health coverage (both employer and employee portions). Filers see a large dollar amount — often $15,000 to $25,000 — and fear they need to report it as income. Code DD exists solely for ACA reporting. It is not included in Box 1 and is not taxable. ¹ [SOURCE: IRS W-2 Instructions — Box 12 code definitions]

Retirement plan contribution limits apply across all employers If you had two jobs that each offered a 401(k), your combined contributions under codes D, E, or similar cannot exceed $23,500 for 2025 (or $31,000 if you are 50 or older, or $34,750 if you are 60 to 63 under the SECURE 2.0 super catch-up provision). Each employer has no way to know what you contributed elsewhere. Exceeding the limit creates an excess deferral that must be withdrawn before your tax filing deadline or it gets taxed twice. ² [SOURCE: IRS Notice 2024-80 — 401(k) contribution limits]

Watch out for this

Treating Box 12 amounts as additional income to report. Most Box 12 codes represent amounts already included in Box 1, amounts deliberately excluded from Box 1, or purely informational amounts. Adding them to your income double-counts them. The only Box 12 amounts that require separate action are excess deferrals and certain amounts tied to Form 4137 or Form 8959.

Related lines on your return

• Box 12b, 12c, 12d — Form W-2 — Continuation boxes for additional codes; same format as 12a
• Box 1 — Form W-2 — Most Box 12 amounts are either already in or deliberately excluded from Box 1
• Box 13 — Form W-2 — Retirement plan checkbox; checked if any Box 12 code indicates a retirement plan