Box 12 Codes That Matter

The Garcias came in together this year. Mrs. Garcia had her W-2 from her retail job. She slid it across the desk and pointed at Box 12.

“What’s this DD code?” she asked. “It says $14,200. Does that mean I owe something on it?”

The preparer shook her head. “No — that one’s informational. DD is the cost of your employer-sponsored health insurance. The IRS requires employers to report it, but you don’t pay tax on it and it doesn’t change anything on your return.”

“Then why is it there?”

“Because Congress wanted the data,” the preparer said. “The important code is the D. Look — D: $3,800. That’s your 401(k) contribution. That one already reduced your Box 1, so it’s been reducing your taxable income all year.”

Box 12 on the W-2 is a collection of letter codes, each followed by a dollar amount. There are over 30 possible codes. You do not need to memorize all of them. You need to recognize the ones you will see every week in a real tax office and know which ones affect the return and which ones are just informational. That’s what this lesson teaches.

Each Box 12 entry has two parts: a letter code and a dollar amount. The code tells you what the amount represents. Some codes represent income that affects the return. Some codes represent pre-tax deductions already excluded from Box 1. Some are purely informational and change nothing on the return.

The W-2 has up to four Box 12 entries (labeled 12a, 12b, 12c, 12d). Some clients have none. Many W-2s have two or three. Occasionally you’ll see four. Read all of them.

Code D — Traditional 401(k) Contributions. The most common Box 12 code. Reports the employee’s pre-tax contributions to a traditional 401(k) plan. This amount has already been excluded from Box 1, so it has already reduced taxable income. You do not deduct it again. But the amount is important for two reasons: (1) it confirms the retirement plan box in Box 13 should be checked, which affects IRA deductibility, and (2) verify the contribution did not exceed the annual limit ($23,500 in 2025; $31,000 if the employee is 50 or older). Excess contributions are taxable.

Code DD — Cost of Employer-Sponsored Health Insurance. Informational only. Reports the total cost of the employee’s employer-sponsored health coverage — both the employer’s share and the employee’s share. Does not affect the return. Do not enter it anywhere. Do not deduct it. Mrs. Garcia’s $14,200 changes nothing on her return. This is the code that confuses clients most because the number is large and they assume it must mean something.

Code W — Employer HSA Contributions. Reports contributions made to the employee’s Health Savings Account by the employer (and sometimes pre-tax employee contributions made through payroll). This amount feeds into Form 8889 (HSA reporting) and affects whether additional HSA contributions can be deducted. We cover HSAs in Lesson 5.

Code C — Group Term Life Insurance Over $50,000. If an employer provides more than $50,000 of group term life insurance, the cost of the excess coverage is taxable income. Code C reports that taxable amount. It is already included in Box 1, so you don’t add it again — but it is also subject to Social Security and Medicare tax, which is why it appears in Box 12 separately. Uncommon for most of your clients but worth recognizing.

Code AA — Roth 401(k) Contributions. Reports employee contributions to a Roth 401(k). Unlike Code D (traditional 401(k)), Roth 401(k) contributions are made with after-tax dollars, so they are NOT excluded from Box 1. The amount is informational — it tells you the client made Roth contributions, but it doesn’t change their taxable wages. Important for retirement planning discussions but does not affect the current year return directly.

Code BB — Roth 403(b) Contributions. Same as AA but for 403(b) plans, typically used by hospitals, schools, and nonprofits. Same treatment: after-tax, informational on the W-2, does not reduce Box 1.

Code E — 403(b) Traditional Contributions. Same concept as Code D but for 403(b) plans. Pre-tax, already excluded from Box 1. Verifies the retirement plan checkbox in Box 13.

Code G — 457(b) Contributions. Government deferred compensation plans. Pre-tax. Same concept as D — already excluded from Box 1. Government employees and some nonprofit employees.

Code S — SIMPLE IRA Contributions. Pre-tax contributions to a SIMPLE IRA retirement plan. Common with small employers. Already excluded from Box 1.

Code P — Excludable Moving Expense Reimbursements. Rarely seen since the 2017 tax law changes limited this exclusion to active duty military members. If you see Code P on a non-military client’s W-2, flag it and verify.