Earning $0 or $100,000 in Your Final Year Barely Moves a 66-Year-Old’s Social Security, But It Can Raise Medicare Two Years Later

The Worry That Shows Up on the SSA Screen

A 66-year-old logs into the Social Security website to file. The final working year paid roughly half the usual salary, plus dividends and interest from a taxable brokerage account. The site asks them to confirm that low earned-income figure, and suddenly the question hits: did I just torpedo my own benefit by easing off work this year?

This worry shows up routinely in online retirement discussions, including a recent r/SocialSecurity thread where one filer compared a hypothetical final year of $0 versus $100,000 and was surprised that the projected check barely moved. The relief is real, and so is the twist underneath it, which has nothing to do with Social Security and everything to do with Medicare two years later.

Why a Soft Final Year Almost Never Hurts the Check

Social Security retirement benefits are based on your highest 35 years of wage-indexed earnings, with adjustment of past wages stopping at age 60. After that, additional years enter the formula at face value and only count if they beat one of the years already in your top 35.

For someone who spent decades earning a steady professional salary, year 36 of work competes against 35 already-strong years. A half-salary final year at 66 usually does not crack the lineup. To see why, consider a retiree with 35 prior years averaging $75,000 in wage-indexed earnings. A final year at $0 leaves the average unchanged. A final year at $100,000 replaces the weakest year in the lineup only if that year was lower than $100,000 in today’s dollars, and for most career professionals, the weakest of their top 35 was still a strong one. Either way, the projected monthly check at 66 barely shifts between the two scenarios, far less than the size of that final paycheck would suggest. That is the relief.

Investment income, meaning dividends, interest, and capital gains, does not count toward the benefit calculation at all, only FICA-covered wages and self-employment income do. The Social Security Administration (SSA) does not look at a tax return to set your check, so waiting to file until April changes nothing. If you keep working after claiming and a future year becomes a new top-35, the agency recalculates upward automatically.

Confirm the low number on the screen, file when planned, and move on.

The Real Catch Lives at Medicare

While a big earnings or investment-sale year does little for the Social Security benefit, it inflates the modified adjusted gross income (MAGI). Medicare uses MAGI from two years earlier to decide whether someone owes an Income-Related Monthly Adjustment Amount (IRMAA) on Part B and Part D.

In 2026, IRMAA surcharges begin once MAGI crosses roughly $109,000 for a single filer or $218,000 for a married couple filing jointly. The structure is a cliff: one dollar over a bracket can add hundreds or even thousands of dollars per person for the full year, and the surcharge is pulled straight out of the Social Security deposit.

The classic trap is the retiree who sells a large position to fund a home purchase the year they start Medicare. The Social Security check does not budge from that sale, but two years later the Medicare premium jumps. The income triggered a surcharge without lifting the benefit.

If a life-changing event such as retirement, job loss, or the death of a spouse has dropped your income, the retiree can ask the SSA to use a more recent year for the IRMAA determination by filing form SSA-44.

What to Actually Do Before You File

The benefit calculation is rarely the issue. The Medicare income picture two years out usually is.

1. Pull your earnings history first. Log into your my Social Security account and look at the full year-by-year record. You will usually see at a glance whether a soft final year is in contention for the top 35. Save a copy, since access becomes more cumbersome after you file.
2. Map any big income event against the two-year lookback. If you are between 63 and 65 and considering a Roth conversion, a business sale, or liquidating a brokerage account, check whether spreading the income across two tax years, or pulling it forward by one, keeps you under the IRMAA bracket that will apply when Medicare premiums are set.
3. Know the appeal exists. A surcharge triggered by income you no longer earn is not permanent. Document the life-changing event and ask for a redetermination.

Every household’s numbers land differently. The point is to focus your attention where the dollars actually move: the income picture Medicare will read two years from now, rather than the final paycheck.