Part-Time Work in Retirement: How It Affects Social Security, Taxes, and Medicare

Linda retired at 63. Two years later, she was bored. A former marketing director, she started consulting a few days a week — projects she chose, clients she liked, no office politics.

The problem wasn't the work. The problem was what the income did to her financial picture.

Her part-time income pushed her over the Social Security earnings limit — reducing her monthly checks. It also nudged her MAGI above an IRMAA threshold she hadn't tracked — raising her Medicare premiums. And her combined income pushed 85% of her Social Security benefits into taxable territory.

None of this was catastrophic. But none of it was expected. And it was all preventable with a bit of planning.

Social Security and the Earnings Test

If you're under your Full Retirement Age (FRA) and collecting Social Security, the earnings test applies.

2026 Earnings Test Limits:

Important distinction: Withheld benefits aren't permanently lost. Once you reach FRA, the SSA permanently increases your monthly benefit to account for months when benefits were withheld. You'll eventually recoup the withheld amounts — it just takes time.

The earnings test only applies to earned income — wages and self-employment income. It does not apply to investment income, pension income, rental income, or IRA distributions.

FRA and When the Rules Change

Full Retirement Age depends on your birth year:

Once you reach FRA, you can earn any amount without any reduction in Social Security benefits. For most retirees considering part-time work, FRA is the natural inflection point.

Tax Implications: Social Security Becomes More Taxable

The Social Security taxation formula is based on "combined income" — your adjusted gross income, plus nontaxable interest, plus half of your Social Security benefits.

Taxation thresholds:

Part-time income increases combined income directly. If your Social Security plus other income was already near these thresholds, additional earned income can push more of your Social Security benefits into taxable territory.

Example:

• Social Security: $24,000/year
• IRA distributions: $18,000/year
• Combined income (without work): $30,000 → ~50% of SS taxable

Add $15,000 in part-time wages:

• Combined income: $45,000 → 85% of SS taxable

That's an extra $8,400 in taxable Social Security income — effectively increasing your tax bill by $1,848–$2,016 depending on bracket.

Medicare IRMAA and the Two-Year Lag

IRMAA surcharges on Medicare premiums are based on your income two years ago. This creates a delayed reaction that surprises many retirees.

If you work part-time in 2026 and your MAGI crosses an IRMAA threshold, your Medicare premiums in 2028 will be higher. By then, you may no longer be working — but you're paying for income you earned two years prior.

2026 IRMAA thresholds (approximate):

If your part-time income is moderate — say, $20,000–$30,000 — run the MAGI math before assuming your Medicare premiums are safe.

Does Part-Time Work Increase Your Social Security Benefit?

Surprisingly, yes — potentially. Social Security benefits are based on your 35 highest-earning years, indexed for inflation. If you have fewer than 35 years of earnings, zeros are averaged in. If your part-time income is higher (in indexed terms) than one of your historical low-earning years, it can replace that year and slightly increase your benefit calculation.

The effect is usually modest, but it's worth knowing. If you're still a few years from claiming, even part-time earnings can marginally improve your eventual benefit.

Planning for Part-Time Work in Retirement

A few strategies to make working in retirement financially efficient:

Wait until FRA to claim Social Security if you plan to work. After FRA, there's no earnings test, no benefit withholding, and no need to worry about the interaction.

Track MAGI proactively. Know your IRMAA threshold and monitor where part-time income will land. If you're $5,000 under the threshold, consider whether adjusting your work schedule is worth the Medicare premium savings.

Consider the self-employment structure. Consulting through an S-Corp or LLC can sometimes reduce net self-employment income (and thus MAGI) through business expense deductions. Talk to a tax professional before assuming all income is equivalent.

Model the combined income formula. Before starting part-time work, calculate your projected combined income for Social Security taxation purposes. Knowing this in advance prevents surprises.

Part-time work in retirement can be enormously fulfilling — and financially helpful. It just works best when you understand the interactions before they show up on your tax return.

Work with a retirement advisor to model how part-time income fits into your specific financial picture.