Dan Reiter, CFP®, CPA, CDFA®,
Many pre-retirees assume taxes become simpler once paychecks stop and Social Security begins. But retirement income often comes from multiple sources — including 401(k) withdrawals, pensions, investment accounts, and Social Security benefits — all of which can interact in ways that affect taxable income.
If you’re approaching retirement, you may be wondering why Social Security is taxed and how the taxable portion of your benefits is actually determined. For some retirees, Social Security benefits may become partially taxable depending on factors such as filing status, benefit amount and other income.
In this article, we’ll focus on how Social Security taxation works — including provisional income, the income thresholds used to determine how much of your benefit may be taxable, and the federal tax rate that ultimately applies. Understanding these rules before retirement can help you better anticipate your tax picture and make more informed decisions as you plan.
For more guidance as you prepare, you can also explore our retirement planning resources.
The amount of your Social Security benefit subject to tax is somewhere between 0% and 85%. Note that this is not the rate of tax, but rather the amount of your benefit you may pay tax on.
For many who have little to no income other than Social Security, none of their benefit is subject to income tax. In fact, the Congressional Budget Office estimated that about half of recipients don’t pay tax on Social Security.
Whether you will be responsible for paying taxes on your Social Security depends on:
Generally, the higher your Social Security payments and additional taxable income, the greater likelihood a higher percentage of your benefits will be taxed. Likewise, the fewer deductions and credits you receive, the more tax you will pay.
Your Social Security benefits and income outside of Social Security work together to determine how much of your benefit may be taxable.
To illustrate the relationship conceptually, we find it helpful to use a mental visual. Imagine you are pouring liquid into a bowl.
The liquid represents your Social Security benefit. Now, imagine there is a line on this bowl. Only the Social Security liquid above the line starts to become taxed. If you fully pour out the contents of your cup and the level within the bowl remains below the line, nothing gets taxed.
However, let’s say that you also start pouring a second container into your bowl. This represents all other income subject to tax outside of Social Security. This liquid settles to the bottom of the bowl, while your Social Security rises to the top.
Now a portion of the Social Security is above the taxable line on the bowl. The amount of liquid above the line is the amount subject to tax.
Eventually, the Social Security cup is empty. If the full amount sits above the line, the taxable portion of your benefit reaches its maximum of 85%.
While there is a bit more nuance to the calculation, this exercise should at least help visualize the concept of how Social Security is taxed.
A specific formula is used to determine the amount of Social Security benefits included in taxable income. This formula starts with determining what your “provisional income” is.
Provisional income is the figure used to determine how much of your Social Security benefit is included in taxable income.
Essentially, your provisional income is equal to all taxable income sources other than Social Security, plus any tax-exempt interest received, plus one-half of your Social Security benefits.
For instance, let’s say you and your spouse are married, earn $2,000 in taxable interest, withdraw $24,000 from an IRA, and receive $48,000 from Social Security.
Your provisional income is $50,000: total non-Social Security income of $26,000, plus $24,000 — half your Social Security.
Once your provisional income is determined, your filing status and applicable income thresholds determine how much of your Social Security is taxable.
For married taxpayers who file a joint return (2026):
For single taxpayers (2026):
These thresholds help explain why two retirees receiving the same Social Security benefit can have very different amounts subject to federal income tax.
For example, here’s how the formula works for a married couple who receives $48,000 in Social Security benefits with varying amounts of other taxable income:
Holding the amount of Social Security received constant, as you start adding additional outside income, the greater the amount your Social Security is taxed. As noted, the range of the portion taxed is anywhere between 0% and 85%, where it is capped.
Social Security benefits do not have a separate federal income tax rate. Once the taxable portion of your benefit is calculated, it is added to your other gross income and taxed according to your applicable federal income tax bracket.
The rate of tax that you pay depends on your:
Once the amount of taxable Social Security is determined, it is aggregated with your other gross income sources. In other words, it does not have its own unique tax calculation, nor is it taxed at a different rate than income received from other ordinary sources.
Ordinary income is taxed at your marginal tax rate. Marginal tax rate is defined as the rate of tax you are responsible for paying on your next $1 of taxable income. This generally will vary with what tax bracket you are in.
Taxable income is your gross income minus any tax deductions you have available. As such, your marginal tax rate is a function of your taxable income. Your taxable income is a function of gross income, including the total amount of Social Security benefit that is taxable, and deductions you have available.
This distinction is important: having up to 85% of your Social Security benefits included in taxable income does not mean you pay an 85% tax rate on those benefits.
2026 Tax Brackets. SOURCE: TaxFoundation.org
Understanding how Social Security is taxed is only one part of the equation. The income you receive from retirement accounts, pensions and investments can also affect how much of your Social Security becomes taxable.
For example, taking additional money from a traditional IRA or 401(k) may increase your taxable income and, in some situations, cause a greater portion of your Social Security benefits to become taxable. In an upcoming article, we’ll explore how different retirement income sources can affect the taxation of your Social Security benefits.
Ultimately, understanding how Social Security is taxed can help you see how your benefits fit into your broader retirement income picture. Taxes, withdrawals, pensions and other income sources can work together in ways that affect your tax liability and the income available to support your retirement.
We know Social Security and retirement taxes can get complicated. At Prosperity Planning, we’re here to help you make sense of how the pieces work together and feel more confident in the decisions you make for your retirement. If you’d like to talk through your own situation, schedule an introductory meeting with our team.
Schedule a call with one of our Certified Financial Planner™ (CFP®) professionals today!
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