Many middle-class retirees expect Social Security to function as steady, predictable income. What often isn’t obvious is how easily that income can shrink because of rules that sit outside the benefit calculation.
Income-based Medicare charges, for instance, are a common surprise. A modest increase in taxable income can raise premiums, with the extra cost deducted straight from Social Security. When that happens, a benefit that once felt predictable can leave less room in an otherwise solid retirement plan.
Here’s how that set of rules works, and why it catches so many middle-class retirees off guard.
How the Medicare income test works
Medicare Part B and Part D premiums depend on your modified adjusted gross income (MAGI) from two years earlier, through the Income-Related Monthly Adjustment Amount (IRMAA).
Each year, the Social Security Administration (SSA) compares your past tax return to set income brackets. If your income falls above a threshold, monthly premiums rise automatically. In 2026, couples who earned more than $218,000 in 2024, or individuals above $109,000, pay higher rates.
For example, a couple with a 2024 income of $220,000 (just over the $218,000 joint threshold) pays about $284.10 a month for Part B (instead of $202.90), and about $14.50 extra on Part D. Higher incomes trigger even steeper increases, with top earners paying several hundred dollars more each month.
There’s no separate bill for these charges. If you collect Social Security, the higher Medicare premiums are pulled straight from your benefit. The result shows up as a smaller deposit in your bank account, often without much warning.
Who really has the cheapest auto insurance in your area? Check your zip code here.
Why middle-class retirees are especially vulnerable
It’s easy to think IRMAA only affects very high earners. In reality, the first surcharge kicks in at income levels many middle-class retirees can reach, especially when multiple income sources overlap.
Social Security, a small pension, part-time work, investment income, and required withdrawals from retirement accounts can add up faster than expected. Each source may seem modest on its own, but together they can push total income just over a Medicare threshold.
The problem is that those thresholds do not rise much over time. As prices and incomes slowly climb, more retirees get pulled in. A household that feels comfortably middle class can suddenly face hundreds of dollars more in monthly premiums, even without a major lifestyle change.
Income moves that can push you into IRMAA
IRMAA isn’t triggered by unusual windfalls alone. Ordinary income events can push retirees over the line, especially when they stack up in the same year.
Required minimum distributions (RMDs), for instance, are a common example. Once RMDs begin at age 73, those forced withdrawals can stack on top of Social Security and other income. A larger-than-expected RMD can be enough to push total income over a Medicare threshold.
Other examples include:
- Large withdrawals from traditional IRAs count as income, even when they aren’t required.
- Selling investments, rental property, or inherited assets can create taxable gains in a single year.
- Converting a traditional IRA to a Roth IRA is fully taxable in the year of conversion, and lump sums can spike income.
- Part-time work, consulting income, bonuses, or extra paychecks late in the year can tip income over a cutoff.
- Up to 85% of Social Security benefits can be included in MAGI, which matters in higher-income years.
The catch is how the rule applies. Crossing a threshold by a small amount doesn’t lead to a small surcharge. It moves you into a higher premium tier for the entire year, which can mean hundreds or even thousands more in Medicare costs.
Impact on your take-home check
In 2026, the average retiree saw about a $56 monthly increase from the 2.8% cost-of-living adjustment (COLA). At the same time, the Part B premium rose $17.90, from $185 to $202.90. Because premiums are withheld automatically, nearly a third of the average raise often disappears before retirees see it.
For retirees pushed into an IRMAA bracket, the hit is much bigger. Crossing a threshold can double or even triple Medicare costs for the year, which can wipe out the entire COLA and more. Some people end up paying more in added premiums than the size of their annual raise.
Note that there is a “hold harmless” rule meant to keep net checks from dropping because of Part B increases, but it does not protect everyone. New Medicare enrollees and retirees newly subject to IRMAA pay the higher premiums in full.
Bottom line
Social Security is meant to provide stability in retirement, but some of the rules make it less predictable than people expect. Medicare’s income-based premiums can quietly chip away at monthly benefits, often without much warning.
Knowing how IRMAA works and how a relatively small income increase can lead to higher premiums can help you avoid money mistakes and reduce surprises. When you’re living on a fixed income, even modest changes can feel big, so it pays to understand where those reductions come from before they show up in your check.
Subscribe Today
Unlock the Best Banking Deals and Bonuses
From high-yield savings accounts to cashback checking and sign-up bonuses, we bring you the best banking offers to grow your money smarter.
Author Details
David Maina
David Maina is a seasoned financial writer for FinanceBuzz who has been crafting insightful, accessible, and well-researched content since 2018. Over the years, he has written extensively on a wide range of personal finance topics, including insurance, retirement planning, Medicare, personal loans, Social Security, and tax planning.
