Box 4 on Your W-2: Social Security Tax Explained

The Form W-2, Wage and Tax Statement, is a document employers must send to employees and the Internal Revenue Service (IRS) at the end of each year. This form reports an employee’s annual wages and the amount of taxes withheld from their paychecks. It is a foundational document for completing federal and state income tax returns, providing a clear summary of earnings and tax payments made throughout the calendar year.

What Box 4 Represents

Box 4 of your W-2 shows the total amount of Social Security tax withheld from your paychecks during the year. This withholding is a federal requirement under the Federal Insurance Contributions Act (FICA). The funds collected are directed to the Social Security Administration to fund the Old-Age, Survivors, and Disability Insurance (OASDI) program.

The OASDI program provides a safety net for working Americans and their families. The money you contribute through Social Security tax helps pay for retirement benefits for current retirees, as well as disability benefits for workers who become unable to work. It also provides survivor benefits to the families of deceased workers.

How Box 4 is Calculated

The figure in Box 4 is calculated by applying the 6.2% Social Security tax rate to your Social Security wages, which are reported in Box 3 of the W-2. This rate is applied to your gross wages after certain pre-tax deductions, such as health insurance premiums, but before deductions for retirement plan contributions like a 401(k). Therefore, the wages in Box 3 can sometimes be higher than the federal taxable wages reported in Box 1.

The calculation uses the annual Social Security wage base limit, an earnings threshold set by the Social Security Administration each year. For the 2025 tax year, the wage base limit is $176,100. An employee will pay Social Security tax only on earnings up to this amount.

Once an employee’s year-to-date earnings exceed this limit, withholding stops for the remainder of the year. The maximum amount that should appear in Box 4 for any individual in 2025 is $10,918.20, which is 6.2% of $176,100. If your Box 3 wages are below this threshold, your Box 4 amount will be your Box 3 wages multiplied by 6.2%.

Scenarios Affecting Box 4

An overpayment can occur when an employee works for more than one employer in a single year. Each employer independently withholds Social Security tax up to the annual wage base limit. If the employee’s combined wages from all jobs exceed the threshold, the excess amount can be claimed as a refundable credit on their federal income tax return.

The process is different if a single employer withholds more than the maximum Social Security tax. You cannot claim the overpayment as a credit on your tax return. You must first request a refund for the excess withholding directly from your employer. If the employer is unable to adjust the overcollection, you can file Form 843, Claim for Refund and Request for Abatement, with the IRS.

In some cases, Box 4 may be empty. This occurs for specific classes of workers who are exempt from Social Security tax withholding. Certain state and local government employees who participate in their own retirement systems may be exempt. The exemption also applies to non-resident aliens on specific visa types, such as F-1 or J-1, for work allowed by their visa. Students working at their university may be exempt if they are enrolled at least half-time and the work is secondary to their education.