W-2 Box 4 — Social security tax withheld
The Social Security tax your employer withheld — exactly 6.2% of Box 3 (plus Box 7 tips), capped at 6.2% of the annual wage base.
At a glance — Box 4
- Box name
- Social security tax withheld
- Reports to
- Not reported on 1040 directly (except for excess from multiple employers — Schedule 3, Line 11).
- Check against
- Box 3 × 6.2% (rounded to cents). The maximum equals 6.2% of the Social Security wage base for the year — see year-notes block.
What Box 4 means
Box 4 reports the Social Security tax withheld from your pay during the year. The rate is fixed by statute at 6.2% of Social Security wages (Box 3 + Box 7) up to the annual wage base. Your employer pays a matching 6.2% that does not appear on your W-2.
If Box 4 is not exactly 6.2% of (Box 3 + Box 7), something is off — ask your employer to investigate and, if needed, issue a corrected W-2c.
Tax return implications
- Generally not deducted or credited on your 1040 — it is already-paid FICA tax.
- If you worked multiple jobs and combined Box 4 exceeds the annual maximum (6.2% of the Social Security wage base), you can claim the excess as a credit on Form 1040 Schedule 3, Line 11.
- Self-employed people pay both halves (12.4%) on Schedule SE — if you had both W-2 and self-employment income, Box 3 counts toward the wage base first.
Common pitfalls & things to check
- Additional Medicare Tax (0.9%) does NOT apply to Social Security — don't look for it in Box 4. It's in Box 6 calculations (and on Form 8959).
- Certain state and local government employees with FICA-exempt retirement systems may have $0 in Boxes 3 and 4.
For 2025 returns (filed by April 15, 2026)
- Max Social Security tax per employee
- $10,918.20
- 6.2% of the $176,100 wage base. Combined Box 4 across multiple employers above this amount is refunded via Schedule 3, Line 11.
Values sourced from central tax-year config at build time — update automatically on FY rollover.
Related W-2 boxes
Box 3 — Social security wages
Your wages subject to Social Security tax, capped at the annual wage base. Differs from Box 1 because traditional 401(k) deferrals are not excluded.
Box 1 — Wages, tips, other compensation
Your taxable federal wages for the year — gross pay minus pre-tax deductions like traditional 401(k), Section 125 cafeteria plan contributions, and pre-tax HSA.
Box 2 — Federal income tax withheld
Total federal income tax your employer withheld from your paychecks during the year, based on your Form W-4 elections.
Box 5 — Medicare wages and tips
Your wages subject to Medicare tax. Unlike Social Security, there is no wage base cap — Box 5 can exceed Box 3 on high salaries.
Reconciling your W-2 at tax time? Use the paycheck calculator to verify expected federal, Social Security, and Medicare withholdings on your salary, and the federal income tax calculator to estimate your refund or balance owing before you file.
Sources
W-2 box definitions per IRS General Instructions for Forms W-2 and W-3 and IRC §6051. Rates and thresholds current for tax year 2025 (file by April 15, 2026); 2026 figures included where published.