Working Past 65 by Choice: The Financial Math

Quick answer: Choosing to keep working past 65 moves three financial levers at once, not just your paycheck. Every year you delay claiming Social Security beyond your full retirement age adds roughly 8% to your monthly benefit, and that larger base then compounds with each year’s cost-of-living adjustment. Every year you keep contributing to a workplace retirement account instead of drawing it down can add tens of thousands of dollars to your ending balance, mostly because the balance isn’t being depleted during market swings while you’re also still adding to it. If your job comes with group health coverage from an employer with 20 or more employees, you can typically delay Medicare Part B without a lifetime late-enrollment penalty. Stack those three effects for someone earning around $90,000 a year with a $700,000 retirement account, and three extra working years past 65 can be worth well over $200,000 in added net worth and higher guaranteed lifetime income, before you even count the salary itself.

Why the Math Changed for People Working Past 65 in 2026

A generation ago, 65 was the finish line. It was the age tied to Medicare eligibility, the age most pension plans used as a reference point, and close enough to full retirement age under Social Security that the two dates practically merged in the public imagination. That alignment broke apart slowly, then all at once. Full retirement age has climbed in stages since the 1980s and now sits at 67 for anyone born in 1960 or later, meaning 65 is no longer a milestone tied to full benefits at all — it is simply the year Medicare eligibility begins, sitting two full years before a worker’s Social Security is fully phased in.

At the same time, required minimum distributions from tax-deferred retirement accounts no longer start at 65, or even 70½ the way they did for earlier generations. The SECURE 2.0 Act pushed the RMD starting age to 73 for most people reaching that age in the current decade, with a further move to 75 scheduled for 2033. Put those two shifts together and the years from 65 to 70 have become a genuinely open runway: a stretch of time where a worker can keep earning, keep contributing, and keep letting both a Social Security benefit and a retirement account compound, entirely by choice rather than by rule.

That choice is becoming more common for reasons that have little to do with financial distress. Remote and hybrid work removed a lot of the physical toll that used to force people out of the workforce. Many professionals in their mid-60s are healthier, more engaged, and more valuable to their employers than the retirement norms built in the 1960s ever anticipated. Surveys from the Employee Benefit Research Institute have repeatedly found that a meaningful share of workers who stay past 65 say they do it because they enjoy the work or want to stay mentally active, not because they have no other option. What often goes missing from that decision, though, is a clear picture of exactly how much the choice is worth in dollars, and exactly which levers are doing the work.

The Three Levers Working Past 65 Pulls at Once

Working past 65 does not produce one financial effect. It produces three, and they interact with each other in ways that are easy to underestimate if you only look at the extra paycheck.

Delayed Retirement Credits Stack on Top of Inflation Adjustments

Social Security rewards patience with a specific, published formula. For every month you delay claiming past full retirement age, up to age 70, your benefit grows by roughly two-thirds of one percent — about 8% for a full year of delay. That growth is not a one-time bonus tacked onto your original benefit; it becomes the new base that every future cost-of-living adjustment is calculated against. A person whose full retirement age benefit is $2,800 a month and who waits a single extra year sees that amount grow to roughly $3,024 before any inflation adjustment is even applied. The following year’s COLA lands on the larger $3,024 figure, not the original $2,800, which is why the gap between claiming early and claiming late widens every single year rather than staying fixed.

This only works one direction. Delayed retirement credits stop accumulating entirely at age 70, so there is no financial reason to put off filing once you cross that birthday — a detail retirees sometimes miss and end up leaving money on the table for no benefit at all. For a closer look at how these credits interact with each year’s cost-of-living adjustment, this guide to delaying Social Security through 2026’s inflation adjustments breaks the compounding down year by year.

A Working Paycheck Buys Your Portfolio Time It Would Otherwise Lose

The second lever is less visible but often larger in dollar terms. A retiree drawing 4% a year from a portfolio is pulling money out during every market cycle, good or bad, and that withdrawal compounds against them the same way a contribution compounds in their favor. A worker who delays retirement removes that withdrawal entirely for however many extra years they work, and in most cases keeps adding new contributions and an employer match on top. The account is being fed from two directions during the working years and drained from zero, which is a very different growth trajectory than an account that is simultaneously growing at a market rate of return while shrinking from withdrawals.

The math is straightforward but the size of the gap surprises most people the first time they run their own numbers, which is exactly what the worked example later in this guide walks through step by step.

The Still-Working Exception Can Pause Your RMDs

The third lever is narrower but valuable for the right person. If you’re still employed and you’re not a 5% or greater owner of the company sponsoring your plan, the IRS “still-working exception” lets you delay required minimum distributions from your current employer’s 401(k) or 403(b) until the year you actually retire, regardless of your age. This exception applies only to the plan at your current employer. It does not extend to IRAs, to 401(k) balances sitting at former employers, or to a spouse’s accounts, so a worker with several old 401(k)s scattered across previous jobs will usually still owe RMDs on those balances even while the current employer’s plan is exempt. Rolling old balances into the current employer’s plan before RMDs begin is one of the few legitimate ways to bring those dollars under the exception, though not every plan accepts incoming rollovers, so this needs to be confirmed with the plan administrator rather than assumed.

Medicare Enrollment Timing When You Haven’t Retired

Medicare eligibility begins at 65 regardless of whether you’re still working, and that creates one of the more consequential decisions in this entire calculation: enroll on schedule, or delay because you’re still covered through a job.

The 20-Employee Rule Decides Whether You Can Wait

The deciding factor is the size of the employer providing your group health coverage. If you work for an employer with 20 or more employees, that group plan is considered primary and you’re generally allowed to delay Medicare Part B enrollment without triggering the late-enrollment penalty, using a Special Enrollment Period once the job or the coverage ends. If your employer has fewer than 20 employees, Medicare typically becomes the primary payer at 65 regardless of your job status, and delaying Part B enrollment in that situation usually means gaps in coverage and, eventually, a permanent premium penalty added on top of whatever the standard premium happens to be. That penalty compounds for life: it’s calculated as roughly 10% of the standard premium for each full 12-month period you were eligible but didn’t enroll, and it never goes away once assessed.

Part A, which covers hospital stays, is usually premium-free for anyone with enough work history, so most people sign up for it at 65 even while delaying Part B, since there’s rarely a downside to doing so.

What Happens to Your HSA

Anyone still contributing to a health savings account needs to plan around a rule that catches a surprising number of people off guard: enrolling in any part of Medicare, including just Part A, makes you ineligible to contribute to an HSA going forward, even if you keep working and keep your high-deductible health plan. Because Part A enrollment is often automatic once you claim Social Security, and because it can be retroactive up to six months once you do enroll, workers who want to keep funding an HSA past 65 sometimes need to actively delay both Social Security and Medicare Part A, and stop HSA contributions several months before they eventually do enroll, to avoid an excess-contribution problem the IRS will flag later.

How an Extra Paycheck Reshapes Your Tax Bill After 65

Continuing to earn a salary past 65 doesn’t just add income; it can change how much of your other income gets taxed, particularly once Social Security enters the picture.

Provisional Income and the Social Security Tax Torpedo

If you claim Social Security while still working, the IRS calculates a “combined income” figure — your adjusted gross income, plus nontaxable interest, plus half of your Social Security benefit — and uses it to decide how much of that benefit is taxable. For a single filer, combined income between $25,000 and $34,000 can make up to 50% of the benefit taxable, and anything above $34,000 can push up to 85% of the benefit into taxable territory. For joint filers, those thresholds sit at $32,000 and $44,000. These numbers have never been indexed for inflation since they were set decades ago, so a working paycheck on top of Social Security pushes a larger share of retirees past them every year. This is the effect commonly nicknamed the Social Security tax torpedo, because a single extra dollar of earned income can drag an outsized amount of previously untaxed benefit into taxable income at the same time.

Most people choosing to work past 65 sidestep the sharpest version of this problem simply by not claiming Social Security yet. Delaying the claim means there’s no benefit for the combined-income formula to tax in the first place, which is one more reason the decision to keep working and the decision to keep delaying tend to reinforce each other financially.

IRMAA Surcharges Triggered by Continuing to Earn

A separate tax-adjacent cost shows up through Medicare itself. Once you’re enrolled in Medicare, your Part B and Part D premiums are set using a two-year-old tax return through the Income-Related Monthly Adjustment Amount, or IRMAA. A worker who keeps earning a full salary past 65 while already enrolled in Medicare can trip an IRMAA bracket and pay a meaningfully higher premium than a retiree with the same account balances but no wages. For 2026, the standard Part B premium sits at roughly $206.50 a month, and each IRMAA bracket above that adds a defined surcharge on top, so it’s worth checking your specific income level against the current-year IRMAA table before assuming Medicare costs will stay at the baseline rate while you’re still on a full paycheck.

Meet Maria: Comparing Two Paths From Age 65 to 68

Numbers land better with a concrete person attached to them, so consider Maria, who just turned 65. Her full retirement age is 67, her full retirement age Social Security benefit works out to $2,800 a month, she earns $90,000 a year, and she has $700,000 sitting in her current employer’s 401(k). She’s weighing two paths.

Path A — Retire and claim now. Maria stops working at 65 and claims Social Security immediately. Because she’s filing 24 months before her full retirement age, her benefit is permanently reduced by 5/9 of 1% for each of those months, a reduction of roughly 13.3%. Her monthly check becomes about $2,427 instead of $2,800. To cover her living expenses, she begins drawing 4% a year from her $700,000 balance, or $28,000 annually, while the remaining balance keeps growing at an assumed 6% average annual return.

Path B — Keep working three more years, delay the claim to 68. Maria keeps her job and her salary, keeps contributing $24,500 a year to her 401(k) with an additional $9,000 in employer match, and takes no withdrawals. Because she’s not a 5% owner of the company, the still-working exception means no RMDs apply to this account regardless of her age. She delays her Social Security claim until she turns 68, one year past her full retirement age, earning an 8% delayed retirement credit on top of her $2,800 base before any cost-of-living adjustments are layered on.

The retirement account gap tells a similar story, and it compounds faster than the monthly Social Security difference because it has both contributions and avoided withdrawals working in the same direction. Under Path A, Maria’s $700,000 shrinks by $28,000 a year in withdrawals while growing at 6%, ending near $739,000 after three years, alongside roughly $84,000 already spent from those withdrawals. Under Path B, the same starting balance grows at the same 6% return with no withdrawals and an added $33,500 a year in contributions, ending near $947,000 after three years — a gap of roughly $208,000 in account value alone, on top of the $597-a-month difference in guaranteed lifetime Social Security income.

None of this means Path A is a mistake for everyone. A worker with health problems, a physically demanding job, or no realistic way to keep earning at the same level has good reasons to claim earlier and rely on the account they already have. The point of Maria’s comparison is narrower: for someone who is able and willing to keep working, the financial case for doing so past 65 is usually much larger than the size of the paycheck suggests, because the paycheck is really three separate effects layered on top of each other.

Retire-and-Claim vs. Work-and-Delay, Side by Side

*Assumes a 6% average annual return, applied after each year’s contribution or withdrawal; actual returns vary and are never guaranteed.

Common Mistakes Workers Make Past 65

• Assuming Medicare and Social Security move together. Medicare eligibility starts at 65 no matter what; Social Security’s full benefit age doesn’t arrive until 67 for anyone born in 1960 or later. Treating the two as one deadline leads people to file for benefits earlier than the math supports.
• Skipping Part B enrollment at a small employer. The 20-employee threshold is not a suggestion. Workers at smaller companies who assume their group plan lets them delay Medicare the same way a large employer’s plan would can end up with coverage gaps and a permanent late-enrollment penalty.
• Forgetting the still-working exception doesn’t cover old accounts. A 401(k) from a job you left a decade ago is still subject to RMDs at 73 even while your current employer’s plan is exempt. Leaving old balances scattered across former employers can trigger required withdrawals a worker fully intended to avoid.
• Continuing HSA contributions after Medicare Part A kicks in. Because Part A enrollment can be automatic and retroactive, workers sometimes keep funding an HSA for months after they’ve technically become ineligible, creating an excess-contribution problem that has to be unwound later.
• Claiming Social Security early “just in case,” then working anyway. Filing before full retirement age while still earning above the annual earnings test limit doesn’t just reduce the benefit through the delayed-credit formula; it can also withhold checks outright under the earnings test, for no net gain once the benefit is later recalculated.
• Ignoring IRMAA until the bill arrives. Because IRMAA is based on a tax return from two years earlier, a big earnings year at 65 can trigger a Medicare surcharge that doesn’t show up until age 67, well after the paycheck that caused it has been forgotten.

A Practical Checklist Before You Decide

• Pull your latest Social Security statement at ssa.gov and confirm your actual full retirement age and your estimated benefit at 65, at full retirement age, and at 70.
• Confirm your employer’s headcount with HR to find out whether the 20-employee rule lets you delay Medicare Part B without a penalty.
• Ask your benefits administrator whether your group health plan is considered primary or secondary to Medicare once you turn 65.
• Inventory every retirement account you hold, and note which ones are with your current employer versus a former one, since only the current plan can qualify for the still-working RMD exception.
• Check whether your plan even accepts incoming rollovers if you’re considering consolidating old 401(k) balances to bring them under that exception.
• Set a calendar reminder several months before you plan to claim Social Security or Medicare Part A to stop HSA contributions cleanly.
• Estimate your combined income under the Social Security taxation formula for the year you expect to file, so there are no surprises on the following spring’s tax return.
• Run your own version of the two-path comparison above using your actual salary, contribution rate, employer match, and account balance, rather than relying on generic averages.

Key Takeaways

• Delaying Social Security past full retirement age adds roughly 8% a year to your benefit, and each year’s cost-of-living adjustment compounds on that larger base going forward.
• Working past 65 without drawing down a retirement account, while continuing to contribute, often has a bigger dollar impact than the delayed Social Security credit by itself.
• The still-working RMD exception only applies to your current employer’s plan, not to old 401(k)s or IRAs, so consolidation matters if you want to use it fully.
• Medicare Part B can usually be delayed penalty-free only if your employer has 20 or more employees; smaller employers generally require enrollment at 65 regardless of job status.
• Claiming Social Security while still earning a full salary exposes more of that benefit to taxation and can trigger earnings-test withholding, so most people working by choice are financially better off delaying the claim rather than filing early and working anyway.

Frequently Asked Questions

Does working past 65 automatically increase my Social Security benefit?

Not automatically, but often indirectly. Your benefit is calculated from your 35 highest-earning years, so if a current year of work replaces an earlier lower-earning or zero-earning year in that calculation, your benefit can rise even without any delayed retirement credit. The larger and more predictable increase, however, comes from delaying the claim itself rather than from the extra work history.

Can I still contribute to a 401(k) or IRA after age 65?

Yes. There is no upper age limit on contributing to a workplace retirement plan or a traditional or Roth IRA, as long as you have qualifying earned income. Contribution limits for 2026 allow up to $24,500 in employee deferrals to a 401(k), with an additional catch-up amount for workers 50 and older, and an enhanced catch-up for those between 60 and 63.

What happens if I keep working at 65 but my employer has fewer than 20 employees?

In that situation, Medicare is generally considered the primary payer once you turn 65, regardless of whether you’re still on the job. Delaying Part B enrollment without qualifying employer coverage usually means a gap in primary coverage and a late-enrollment penalty added to your premium for as long as you have Medicare.

Do required minimum distributions ever apply while I’m still working?

They can, depending on which account. The still-working exception only protects your current employer’s 401(k) or 403(b), and only if you’re not a 5% or greater owner of the business. RMDs still apply on schedule, starting at age 73 under current rules, to IRAs and to 401(k) balances held at any employer you’ve already left.

Is it better to claim Social Security at 65 and keep working, or delay the claim while working?

For most people who are working by choice and don’t need the income to cover current expenses, delaying the claim tends to come out ahead. Claiming early while earning above the annual earnings test limit can result in withheld benefits and a permanently reduced monthly amount, while delaying avoids both problems and keeps building toward a larger benefit at full retirement age or beyond.

References

1. Social Security Administration. Retirement Benefits: Full Retirement Age. SSA Publication No. 05-10035.
2. Social Security Administration. Delayed Retirement Credits. Benefit Planner documentation, ssa.gov.
3. Social Security Administration. How Work Affects Your Benefits. Annual earnings test documentation, ssa.gov.
4. Internal Revenue Service. Retirement Topics — Required Minimum Distributions (RMDs). irs.gov.
5. Internal Revenue Service. Retirement Plan and IRA Required Minimum Distributions FAQs, including the still-working exception. irs.gov.
6. Centers for Medicare & Medicaid Services. Medicare & You handbook, current edition, and annual Part B premium and IRMAA announcements.
7. Internal Revenue Service. Publication 969: Health Savings Accounts and Other Tax-Favored Health Plans. irs.gov.
8. Employee Benefit Research Institute. Retirement Confidence Survey, most recent annual release.