What Is Social Security Tax?

Social Security tax is a federal payroll tax in the United States used to fund the Social Security program, which provides retirement, disability, and survivor benefits. The tax is assessed on wages and self-employment income and is mandated by the Federal Insurance Contributions Act (FICA) for employees and the Self-Employment Contributions Act (SECA) for independent earners. It is one component of FICA tax, the other being Medicare tax.

The Social Security program was established in 1935 as part of the Social Security Act and is administered by the Social Security Administration (SSA). The tax collected today is used to pay current beneficiaries, rather than being set aside for individual taxpayers. This pay-as-you-go model means today's workers fund the benefits of today's retirees.

Who Pays Social Security Tax

Both employees and employers are subject to Social Security tax. The tax is split evenly, with each contributing a percentage of the employee’s wages up to a specified annual wage cap. For self-employed individuals, the full amount is paid by the individual, since they function as both employer and employee under SECA rules.

The current Social Security tax rate for employees is 6.2%, with employers also paying 6.2%, making a total of 12.4%. Self-employed individuals pay the full 12.4%, though they may deduct the employer-equivalent portion when calculating their adjusted gross income for federal tax purposes.

Wage Base Limit

Social Security tax applies only to income up to a specific annual limit, known as the wage base. This limit is adjusted annually based on changes in national average wages. Income earned beyond this threshold is not subject to additional Social Security tax, although it may still be subject to Medicare tax and additional Medicare surtaxes, depending on income level.

As of 2025, the Social Security wage base limit is $176,100. This means any earnings above that amount are exempt from Social Security tax, though they are still included in other tax calculations.

Types of Income Subject to the Tax

Social Security tax applies to most earned income, including wages, salaries, bonuses, and commissions. It does not apply to unearned income such as interest, dividends, capital gains, or rental income. Additionally, certain employee benefits—such as employer contributions to health insurance—are not subject to Social Security tax.

Some types of workers are exempt from paying Social Security tax under limited circumstances. This may include certain state and local government employees who participate in alternative retirement systems, some religious group members who opt out for religious reasons, and nonresident aliens in specific visa categories.

Employer Withholding and Reporting

Employers are responsible for withholding the employee portion of Social Security tax from each paycheck and remitting both the employee and employer shares to the IRS. This process occurs through regular payroll tax deposits and is reported on IRS Form 941, the Employer's Quarterly Federal Tax Return. Employers also report annual wage and tax information to the Social Security Administration using Form W-2.

Accurate withholding and reporting are essential because these records affect a worker’s eligibility for future Social Security benefits. Inaccurate records may result in lower benefit calculations or delays in benefit eligibility.

Self-Employment and SECA Tax

Individuals who work for themselves, including sole proprietors, freelancers, and independent contractors, are not subject to FICA but instead pay self-employment tax under SECA. The self-employment tax rate includes both the Social Security and Medicare tax components. The Social Security portion remains 12.4% on net earnings up to the wage base limit. These individuals report and pay the tax annually using IRS Schedule SE (Form 1040).

Self-employed individuals can deduct half of the SECA tax from their gross income when filing income taxes, which helps account for the fact that they are responsible for both the employee and employer portions.

Role in Benefit Eligibility

Paying Social Security tax is directly linked to earning credits toward future Social Security benefits. Workers earn up to four credits per year based on their income, and a minimum of 40 credits (typically equivalent to 10 years of work) is required to qualify for retirement benefits. Similar rules apply to disability and survivor benefits.

The amount of Social Security tax paid over a career, along with average indexed monthly earnings, determines the amount of benefits a worker is eligible to receive upon retirement or disability.

The Bottom Line

Social Security tax is a foundational component of the United States' social insurance system. It ensures funding for retirement, disability, and survivor benefits for millions of Americans. Workers contribute through payroll or self-employment taxes, and those contributions determine both eligibility and benefit amounts. While capped annually by the wage base limit, the tax is mandatory for most workers and plays a critical role in the long-term financing of the Social Security program.