Form W-2 Box Decoder Calculator 2026 β All Boxes Explained
Decode every box on your W-2. Calculate expected Social Security cap check, Additional Medicare Tax verification, Box 1 vs Box 3 reconciliation, and all Box 12 codes. 2026 SS wage base $184,500.
Enter Your W-2 Box Values
$
Taxable wages for federal income tax $
$
Capped at $184,500 in 2026 $
Should be exactly 6.2% of Box 3 $
No cap β should be greater than or equal to Box 3 $
Should be 1.45% of Box 5 (plus 0.9% on wages over $200K) $
$
Informational only β not taxable $0 gap
Box 1 vs Box 3 Difference
OK
Social Security Tax Check
OK
Medicare Tax Check
Not Reached
SS Wage Base ($184,500)
W-2 Box-by-Box Analysis
Understanding Your W-2
The W-2 is your annual wage and tax statement. Boxes 1 through 6 contain the core wage and FICA tax data. Box 12 encodes pre-tax benefits and other special amounts. Box 14 is employer-defined informational data.
Why Box 1 May Differ from Box 3
Box 3 (SS Wages) = Box 1 (Fed Wages) + Pre-tax 401k/403b/457 (Code D/E/G)
Box 5 (Medicare Wages) = Box 3 (SS Wages) β same unless SS cap reached
2026 SS Cap: $184,500 per employee | Box 4 max: $11,439
Box 5 (Medicare Wages) = Box 3 (SS Wages) β same unless SS cap reached
2026 SS Cap: $184,500 per employee | Box 4 max: $11,439
Sources and References (click to expand)
Extended
Box 12 Code Decoder and W-2 Reconciliation
Full Box 12 code lookup with taxability, where reported, and reconciliation table. SVG bar chart of Box 1, 3, and 5 wage differences.
Select a Box 12 code to decode its meaning, taxability, and where it flows on your tax return.
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Visual comparison of Box 1, Box 3, and Box 5 β shows pre-tax deduction effects.
Verify your W-2 FICA taxes are correct based on the boxes you entered.
Frequently Asked Questions
Why is Box 1 (federal wages) lower than Box 3 (Social Security wages) on my W-2?
Box 1 shows your wages subject to federal income tax withholding. Box 3 shows wages subject to Social Security tax. The difference is usually pre-tax benefit deductions that reduce Box 1 but NOT Box 3. Common examples: 401(k) and 403(b) contributions (Box 12 code D) reduce Box 1 but not Box 3. However, Section 125 cafeteria plan deductions (health insurance, FSA, dependent care FSA) reduce BOTH Box 1 AND Box 3. Only 401(k)-type pre-tax deferrals create this gap. So if Box 1 = $75,000 and Box 3 = $80,000, you likely contributed $5,000 to a 401(k).
What are the most common Box 12 codes and what do they mean?
Box 12 reports several important amounts. Code D: pre-tax 401(k) elective deferrals (reduces Box 1, not Box 3). Code DD: cost of employer-sponsored health coverage (informational only, not taxable). Code W: employer contributions to Health Savings Account (HSA). Code E: 403(b) elective deferrals. Code G: 457(b) government plan deferrals. Code AA: designated Roth 401(k) contributions (after-tax, included in Box 1). Code BB: designated Roth 403(b). Code EE: designated Roth 457. Code S: SIMPLE retirement account contributions. Code C: taxable cost of group-term life insurance over $50,000. Code J: nontaxable sick pay. Code R: employer contributions to Archer MSA.
How do I check if the right amount of Additional Medicare Tax was withheld?
The Additional Medicare Tax of 0.9% applies to wages exceeding $200,000 ($250,000 for MFJ). Employers withhold the 0.9% on wages over $200,000 per employee per employer β but this threshold is per-employer, not per-household. If you have multiple employers or a spouse with wages, the combined wages may exceed the $250,000 MFJ threshold. In that case, you may owe additional tax not withheld by any employer. Box 5 (Medicare wages) minus Box 6 (Medicare tax) should equal 1.45% for the standard rate plus 0.9% on amounts over $200,000. You can verify using Form 8959.
What does Box 14 contain and when does it affect my taxes?
Box 14 is an informational catchall. Employers use it to report items not required elsewhere. Common Box 14 entries include: state disability insurance (SDI) paid by employee (may be deductible as a state tax on Schedule A), union dues, employee share of health insurance premiums (if not a Section 125 plan), uniform allowances, educational assistance, charitable contributions via payroll deduction, and FMLA amounts. Most Box 14 items are informational only and do not affect your federal tax return. However, SDI or similar taxes may be SALT deductible if you itemize. Some states require specific Box 14 reporting.
What is the 2026 Social Security wage base and Box 3 cap?
For 2026, the Social Security wage base (maximum earnings subject to SS tax) is $184,500. Box 3 of your W-2 cannot exceed $184,500. Box 4 should equal exactly 6.2% of Box 3 (employee SS tax). If Box 3 exceeds $184,500 or Box 4 exceeds $11,439 ($184,500 x 6.2%), contact your employer to correct the W-2 β this is an error. Box 5 (Medicare wages) has no cap and can exceed $184,500. Box 6 should equal 1.45% of Box 5, plus an additional 0.9% on any amounts over $200,000.