4 — Social Security Tax Withheld Updated for tax year 2025

What this line means

The amount of Social Security tax (FICA) your employer withheld from your paychecks during the year. The rate is 6.2% of your Social Security wages (Box 3), up to the wage base cap of $176,100 for 2025. Your employer paid an additional 6.2% on your behalf — that amount does not appear on your W-2.

Does this apply to you?

• You earned wages and your employer withheld Social Security tax from every paycheck
• You want to verify that Box 4 equals 6.2% of Box 3
• You had multiple employers and need to check whether total Social Security tax withheld exceeded the maximum

Easy to overlook

Your employer matches your contribution dollar for dollar Box 4 shows only the employee portion. Your employer paid an identical 6.2% on your wages — you just never see it on your W-2 or your paycheck. The combined 12.4% funds Social Security. Self-employed workers pay the full 12.4% themselves through self-employment tax, which is why switching from W-2 employment to self-employment causes a noticeable tax increase. ¹ [SOURCE: SSA — 2025 FICA rate 6.2% employee / 6.2% employer]

Multiple W-2s can mean overpaid Social Security tax Each employer withholds independently up to the $176,100 cap. If Employer A paid you $120,000 and Employer B paid you $80,000, you had Social Security tax withheld on $200,000 — but only $176,100 is subject to the tax. The excess withholding ($23,900 x 6.2% = $1,481.80) is refundable when you file your 1040. ² [SOURCE: IRS Schedule 3 — excess Social Security tax credit]

Watch out for this

Confusing Box 4 (Social Security tax) with Box 2 (federal income tax). Box 2 is a prepayment toward your income tax that gets reconciled on your 1040. Box 4 is a flat-rate payroll tax with no reconciliation — you do not get it back unless you exceeded the wage base across multiple employers. Filers sometimes add Box 4 to their withholding on Line 25a, which overstates their payments.

Related lines on your return

• Box 3 — Form W-2 — The wages this tax was calculated on (Box 4 should equal 6.2% of Box 3)
• Box 6 — Form W-2 — Medicare tax withheld; a separate payroll tax with no wage cap
• Line 25a — Form 1040 — Federal income tax withheld; Box 4 does not go here