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Social Security tax, also called FICA (Federal Insurance Contributions Act) tax, funds the Social Security program that pays benefits to retirees, disabled workers, and survivors of deceased workers. Both employees and employers pay this tax on wages and self-employment income. The tax rate has remained stable for many years: workers pay 6.2% of their wages, and employers match that amount with another 6.2%. Self-employed individuals pay the full 12.4% themselves.
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The Social Security Administration sets an annual wage base limit, which is the maximum amount of income subject to Social Security tax in a given year. Any earnings above this limit are not subject to the Social Security tax, though they may be subject to Medicare tax. This wage base limit changes each year based on average wage growth in the economy. Understanding this limit matters because it affects how much you and your employer pay into the system during the year.
In 2025, the Social Security wage base limit is $168,600. This means that if you earn $168,600 or less during the year, all of your wages are subject to Social Security tax. If you earn more than $168,600, only the first $168,600 is subject to the tax. For example, if you earn $200,000 in 2025, Social Security tax applies to $168,600 of that income, not the full $200,000.
The wage base limit typically increases year after year because the Social Security Administration adjusts it based on national average wage trends. In 2024, the limit was $168,600, which means it remained the same as 2025 in this case—though most years see an increase. Knowing the current year's limit helps you and your employer calculate correct tax withholdings on paychecks throughout the year.
Practical takeaway: Check your pay stub to confirm that Social Security tax has been withheld only on earnings up to $168,600 in 2025. If you have multiple jobs or changed jobs during the year, monitor your combined earnings to understand your total Social Security tax responsibility.
The wage base limit functions as a ceiling on taxable earnings for Social Security purposes. To illustrate how it works in practice, consider several scenarios. If you earn a salary of $100,000 in 2025, all $100,000 is subject to the 6.2% Social Security tax, totaling $6,200 in taxes. If you earn $168,600, all of that amount is taxed at 6.2%, totaling $10,453.20. However, if you earn $200,000, only $168,600 is subject to Social Security tax, resulting in $10,453.20 in taxes—the same amount as someone earning $168,600, despite earning significantly more.
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This system means that higher earners pay a smaller percentage of their total income toward Social Security tax. For someone earning $168,600, the tax represents 6.2% of their income. For someone earning $336,000 (double that amount), the tax of $10,453.20 represents only 3.1% of their total income. This is why Social Security has a regressive tax structure for earnings above the wage base limit.
The wage base limit also matters for people with multiple jobs or side income. If you work two part-time jobs and earn $100,000 from one and $80,000 from the other (totaling $180,000), you'll pay Social Security tax on all wages up to $168,600 combined. This means you pay taxes on $168,600 of your $180,000 total earnings, with $11,400 above the limit not subject to Social Security tax.
Employers are responsible for withholding the correct amount of Social Security tax from employee paychecks based on the wage base limit. However, if you work for multiple employers during the year, it's possible to overpay Social Security tax if your combined earnings from all jobs exceed the wage base limit. The IRS allows you to claim a credit for excess Social Security tax paid when you file your annual tax return, which means you can recover the overpayment.
Practical takeaway: Track your year-to-date earnings from all employers to monitor whether you're approaching or exceeding the $168,600 wage base limit. If you have multiple jobs, keep records of Social Security taxes withheld from each employer to identify any overpayment when filing taxes.
While Social Security tax applies only to earnings up to the wage base limit, Medicare tax works differently. Medicare tax is a separate payroll tax that funds the Medicare health insurance program for people age 65 and older. Unlike Social Security tax, Medicare tax has no wage base limit—it applies to all wages and self-employment income, regardless of how much you earn.
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In 2025, the Medicare tax rate is 2.9% for employees and employers combined (1.45% each). Like Social Security tax, employers withhold this from paychecks and contribute a matching amount. Self-employed individuals pay the full 2.9%. Because there is no wage base limit for Medicare tax, someone earning $300,000 pays Medicare tax on all $300,000, not just a portion.
In addition to the standard Medicare tax, there is an Additional Medicare Tax that applies to high earners. This extra tax was introduced in 2013 as part of healthcare reform. The Additional Medicare Tax rate is 0.9%, and it applies to wages exceeding certain thresholds. For single filers, the threshold is $200,000. For married couples filing jointly, it's $250,000. For married individuals filing separately, it's $125,000. If your income exceeds these amounts, you pay an extra 0.9% Medicare tax on the earnings above the threshold.
To illustrate, a single person earning $250,000 in 2025 would pay the standard 1.45% Medicare tax on all $250,000, plus an additional 0.9% Medicare tax on the $50,000 that exceeds the $200,000 threshold. This results in an additional $450 in taxes ($50,000 × 0.9%). Many high earners are subject to this Additional Medicare Tax, and employers should be withholding it from paychecks automatically, though some self-employed individuals must calculate and pay it themselves when filing taxes.
Practical takeaway: Review your pay stub to confirm that both standard Medicare tax and Additional Medicare Tax (if applicable) are being withheld correctly. If you're self-employed or have income that isn't subject to automatic withholding, set aside money to cover your Medicare tax obligations when you file your annual return.
Self-employed individuals—including freelancers, business owners, and independent contractors—must pay self-employment tax rather than having an employer withhold payroll taxes. Self-employment tax covers both the employee and employer portions of Social Security and Medicare taxes. In 2025, the self-employment tax rate is 15.3%, consisting of 12.4% for Social Security and 2.9% for Medicare.
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The calculation for self-employment tax begins with your net self-employment income, which is your business income minus business expenses. However, you don't pay self-employment tax on your entire net income. The Social Security portion applies only to net earnings up to the wage base limit of $168,600 in 2025. The Medicare portion applies to all net self-employment income with no limit, plus the Additional Medicare Tax applies to earnings above the income thresholds mentioned previously.
To calculate self-employment tax, you first determine your net self-employment income. Let's say you operate a consulting business with gross income of $200,000 and business expenses of $50,000, giving you net income of $150,000. You would calculate Social Security self-employment tax on the full $150,000 (since it's below the $168,600 limit) at 12.4%, resulting in $18,600. You would also calculate Medicare self-employment tax on the full $150,000 at 2.9%, resulting in $4,350. Your total self-employment tax would be $22,950.
Self-employed individuals can deduct half of their self-employment tax as an adjustment to income when filing their annual tax return. In the example
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