The History of the Medicare Program
The Medicare program and its corresponding tax have been around since 1965, when President Lyndon Johnson signed the Medicare and Medicaid Act, also known as the Social Security Amendments, into law. The program was initially designed to provide health care benefits to senior citizens and to low-income individuals, but the Social Security Amendment of 1972 expanded the program to cover people with permanent disabilities and end-stage renal disease. More benefits have been added over the years, including coverage of prescription drugs.
The Medicare Hospital Insurance Tax
Unlike the Social Security tax—the other component of the Federal Insurance Contributions Act, or FICA, taxes—all of your wages and business earnings are subject to at least the 2.9% Medicare hospital insurance program tax. Social Security has an annual wage limit, so you pay the 6.2% tax only on income up to a certain amount: $160,200 in 2023. Income after that is not subject to Social Security tax (known officially as Old-Age, Survivors, and Disability Insurance [OSADI]). Half the Medicare tax is paid by employees through payroll deductions, and half is paid by their employers. In other words, 1.45% comes out of your pay and your employer then matches that, paying an additional 1.45% on your behalf, for a total of 2.9%.
Medicare as Part of Self-Employment Tax
You’ll take something of a double hit on the Medicare tax if you’re self-employed. You must pay both halves of the tax because you’re the employee and the employer. Together with also paying both halves of the Social Security tax, this obligation is known as the self-employment tax and amounts to 15.3% of your income. The IRS does throw self-employed individuals a bit of a bone. You’re allowed to deduct half your self-employment tax as an adjustment to income on your Form 1040 tax return. Unlike many other deductions, this one reduces your adjusted gross income (AGI), which is a good thing. Many tax breaks depend on your AGI falling below certain limits.
The Additional Medicare Tax
Some high-income taxpayers must pay an extra Medicare tax over and above the 2.9% rate. The Additional Medicare Tax (AMT) was added by the Affordable Care Act (ACA) in November 2013. The ACA increased the Medicare tax to 3.8% for taxpayers whose incomes are over a certain threshold based on their filing status.
Payroll Withholding for the AMT
Employers might not always be aware that an employee is subject to withholding for the AMT. For example, if an employee works more than one job, their incomes from Employer A and Employer B might both fall under the threshold individually, so neither employer would withhold this tax. Any shortfall to withholding must be paid by the taxpayer at tax time. Employers can be subject to penalties and interest for not withholding the AMT, even if the oversight was due to understandable circumstances.
The Net Investment Income Tax
There was a time when investment income wasn’t subject to the Medicare tax, but that changed with the Affordable Care Act as well. A Medicare contribution tax of 3.8% now additionally applies to “unearned income”—that which is received from investments, such as interest or dividends, rather than from wages or salaries paid in compensation for labor or self-employment income. This tax is called the Net Investment Income Tax (NIIT). Tax-exempt interest income, such as from an investment in municipal bonds, is exempt from the NIIT, as are withdrawals from certain retirement plans and certain life insurance proceeds. But required minimum distributions taken from traditional IRAs, 401(k) plans, or 403(b) plans are included in your modified adjusted gross income (MAGI), and this can be an important distinction. The 3.8% rate applies to the lesser of your net investment income or the amount by which your MAGI exceeds a threshold amount. For 2023, the threshold amounts are the same as for the AMT (see the table above).
The Bottom Line
Many taxpayers only have to deal with that first 2.9% flat rate Medicare tax, but you could end up paying more than this percentage to Medicare if you’re a high earner with investment income.
