For years, savings accounts paid almost nothing. Now high-yield savings accounts and CDs have been paying around 4%, and many retirees are earning real interest again. That is good news. But few people realize that the interest can do more than add a little to their tax bill.
Interest income can make more of your Social Security benefit taxable and, at higher incomes, raise your Medicare premiums. It does not, however, affect the Social Security earnings limit.
This guide explains each effect in plain terms, with worked examples using 2026 rules.
The short answer
| Question | Answer |
| Is interest from savings and CDs taxable? | Yes, as ordinary income on your federal return. Interest on U.S. Treasury securities is exempt from state income tax. |
| Does it count toward taxes on Social Security? | Yes. Interest is part of the “combined income” formula. Even tax-exempt municipal bond interest counts. |
| Does it count toward Medicare IRMAA surcharges? | Yes. IRMAA is based on modified adjusted gross income, which includes interest and tax-exempt interest. |
| Does it count toward the Social Security earnings limit? | No. Only wages and self-employment income count. |
How interest affects taxes on Social Security
Whether your Social Security benefits are taxed depends on a figure the IRS calls combined income (also called provisional income):
Combined income = adjusted gross income + tax-exempt interest + half of your Social Security benefits
Your adjusted gross income includes pensions, IRA and 401(k) withdrawals, wages, dividends, and interest from savings, CDs and Treasuries.
Then the thresholds apply:
| Filing status | Up to 50% of benefits may be taxable when combined income is | Up to 85% may be taxable when combined income is above |
| Single | $25,000 to $34,000 | $34,000 |
| Married filing jointly | $32,000 to $44,000 | $44,000 |
These thresholds were set decades ago and have never been adjusted for inflation, which is why more retirees cross them every year.
Why each dollar of interest can count almost twice
Once your combined income is above the lower threshold, each extra dollar of income can make 50 cents or 85 cents of your Social Security taxable as well. So $1,000 of interest might add $1,500 or even $1,850 to your taxable income. Planners sometimes call this the tax torpedo.
Example 1: A single retiree
Linda is 70 and single. She receives $24,000 a year in Social Security and $18,000 from a pension. She moves $100,000 into a CD paying 4%, which earns $4,000 in interest.
| Without the CD interest | With $4,000 of CD interest | |
| Combined income | $30,000 | $34,000 |
| Taxable Social Security | $2,500 | $4,500 |
| Total taxable income before deductions | $20,500 | $26,500 |
The $4,000 of interest raised Linda’s taxable income by $6,000, because it also made another $2,000 of her Social Security taxable.
Does she owe tax? In 2026, a single filer 65 or older gets the $16,100 standard deduction, a $2,050 additional deduction for age, and up to $6,000 from the new senior deduction, for a total of $24,150. Without the CD, Linda owes nothing. With it, about $2,350 is taxable at 10%, so she owes around $235. That is still a good trade for $4,000 of interest, but it is more tax than she expected.
Example 2: A married couple
Tom and Maria are both 68. They collect $40,000 a year in combined Social Security and take $40,000 a year from their IRAs. They have $250,000 in savings and CDs earning 4%, or $10,000 a year.
| Without the interest | With $10,000 of interest | |
| Combined income | $60,000 | $70,000 |
| Taxable Social Security | $19,600 | $28,100 |
| Total taxable income before deductions | $59,600 | $78,100 |
| Deductions (standard, age 65+ and senior deduction) | $47,500 | $47,500 |
| Taxable income | $12,100 | $30,600 |
| Estimated federal tax | about $1,210 | about $3,176 |
Their $10,000 of interest raised their federal tax by about $1,966, nearly 20% of the interest they earned, even though their top tax bracket is only 12%. The reason is that it also made another $8,500 of their Social Security taxable.
Tax figures use 2026 federal brackets and deductions and are simplified. State taxes are not included.
Who this affects most
The interest effect on Social Security taxes hits hardest in a middle band of incomes, not at the top or bottom.
- Lower incomes: If your combined income stays below $25,000 (single) or $32,000 (married), none of your benefits are taxed, and modest interest will not change that.
- Middle incomes: Retirees with pensions or IRA withdrawals that put them between the thresholds feel it most, because each dollar of interest pulls extra Social Security into taxable income. This is where many middle-class retirees sit.
- Higher incomes: Once 85% of your benefits are already taxable, extra interest is simply taxed at your normal rate. At this level, the bigger risk is crossing an IRMAA threshold.
If you are in your 50s and building up cash savings before retirement, it helps to know which band you are likely to land in. It can shape where you hold your savings once you retire.
How interest affects Medicare premiums (IRMAA)
Medicare Part B and Part D premiums rise for people with higher incomes. The extra charge is called the Income-Related Monthly Adjustment Amount, or IRMAA.
Key points:
- IRMAA is based on your modified adjusted gross income (MAGI) from two years earlier. Your 2026 premiums are based on your 2024 tax return.
- MAGI for IRMAA is your adjusted gross income plus tax-exempt interest. So both CD interest and municipal bond interest count.
- For 2026, surcharges start when MAGI is above $109,000 for single filers and $218,000 for married couples filing jointly.
- IRMAA works like a cliff. Going $1 over a threshold triggers the full surcharge for that tier.
In 2026, the standard Part B premium is $202.90 a month. In the first IRMAA tier, it rises to $284.10, and Part D adds a surcharge of $14.50. For a married couple both on Medicare, crossing that first threshold costs about $2,297 a year in extra premiums.
If a year of large interest income, or interest combined with a big IRA withdrawal or home sale, pushes you just over a threshold, that one year can raise your Medicare costs two years later.
The new $6,000 senior deduction does not help here. It reduces taxable income but does not lower the MAGI figure used for IRMAA or the combined income used for Social Security taxation.
What about the Social Security earnings limit?
If you claim Social Security before full retirement age and keep working, benefits can be temporarily withheld when your earnings pass a yearly limit. Only wages and net self-employment income count toward that limit. Interest, dividends, pensions and IRA withdrawals do not.
Ways to manage the effect
You should not avoid interest because of taxes. Keeping cash in a 0.01% account to dodge a small tax is a losing trade. But a few moves can reduce the bite.
- Hold some savings inside an IRA or Roth IRA. CDs and money market funds held in a retirement account do not create taxable interest each year. Qualified Roth withdrawals do not count toward combined income or IRMAA.
- Use Treasury bills or Treasury money market funds if you live in a state with income tax. The interest is still federally taxable but exempt from state tax.
- Time CD maturities. Interest is generally taxed in the year it is credited to you. Spreading maturities across years can keep income steadier.
- Watch big income years. If you plan a large IRA withdrawal, Roth conversion or home sale, consider how interest income that year adds to the total.
- Appeal IRMAA if your income dropped. If your income fell because of a life-changing event such as retirement or the death of a spouse, you can ask Social Security to use a more recent year by filing Form SSA-44.
- Adjust your withholding. Many retirees are surprised by a tax bill in April. You can have federal tax withheld from Social Security using Form W-4V.
Frequently asked questions
Does interest income count toward Social Security taxation? Yes. Taxable interest is part of adjusted gross income, and tax-exempt interest is added back, so both count toward combined income.
Does municipal bond interest affect Social Security taxes? Yes. Although municipal bond interest is usually free of federal income tax, it is added in when calculating combined income and MAGI for IRMAA.
Does CD interest count as income for Medicare premiums? Yes. It is part of MAGI, which Medicare uses to decide whether you pay IRMAA surcharges.
Does interest income reduce my Social Security benefit? No. Interest does not reduce the benefit itself or count toward the earnings limit. It can only affect how much of your benefit is taxed and your Medicare premiums.
Sources
- Internal Revenue Service, Publication 915, Social Security and Equivalent Railroad Retirement Benefits
- Internal Revenue Service, 2026 tax brackets, standard deductions and enhanced deduction for seniors
- Centers for Medicare and Medicaid Services, 2026 Medicare Parts B and D premiums and IRMAA
- Social Security Administration, Form SSA-44 and the retirement earnings test
- CBS News, high-yield savings rates, 2026
Examples are simplified and use 2026 federal rules. This article is general information, not tax advice. Consider a tax professional for your situation.
