Retirement Social Security

This Simple Social Security Math Could Make Another Year of Work Pay Off

One calculation could change your retirement timing decision.

By David Maina, CPA , Edited by Laura Hohenstein

Updated May 13, 2026

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Choosing when to retire is rarely simple, but your Social Security record can help narrow the question. Your benefit is based on your 35 highest-earning years, which means a strong year of income now can sometimes replace a weaker year from your past and raise your future monthly check.

That does not mean another year of work always pays off. If your new earnings would not replace one of those lower years, your benefit may stay exactly the same.

Knowing which side of that line you are on can make the choice feel clearer and give your retirement plan a stronger starting point.

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How the 35-year average works

Social Security does not base your benefit on your final salary or your total lifetime earnings. Instead, it looks at your 35 highest-earning years, adjusts each one to account for wage growth over time, adds them all up, and divides by 420, which is the number of months in 35 years.

The result is called your Average Indexed Monthly Earnings, and it is the number your monthly check is built on.

If you worked fewer than 35 years, Social Security fills each gap with a zero and still divides by 420. That means someone with 30 years of work history has five zeros pulling their average down, and even a single missing year quietly reduces the benefit.

Adding a year of real earnings in place of one of those zeros can make a noticeable difference in your monthly check.

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How new earnings can improve your monthly check

An additional year of work improves your benefit only if it earns a place in your top 35, either by filling a zero or replacing a weaker year.

Filling a zero gives you the biggest gain. If you have 34 years on your record and earn $50,000 in one more year, that new year knocks out a zero and adds the full $50,000 to your 35-year total. Divided by 420 months, that works out to roughly $119 more per month, which flows directly into a higher monthly benefit.

Replacing a weak year works the same way, just with a smaller result. If your lowest counted year after indexing was $20,000 and you earn $50,000 in a new year, the difference of $30,000 adds about $71 per month to your average.

The bigger the gap between your new earnings and the year they replace, the bigger the improvement to your benefit.

The years that don't make the top 35

If your new earnings do not beat any of your current top 35 years, that extra year simply gets dropped from the calculation, and your average stays the same.

For someone who has already worked 40 years at consistently strong wages, adding another year at a similar or lower salary will not change the final number. The formula only looks at the top 35, so anything below that threshold falls away.

One detail that is easy to overlook is how the Social Security Administration (SSA) adjusts older earnings before making these comparisons. A salary from 1995 does not compete at its original value. It gets adjusted upward to reflect wage growth since then, which often makes it larger than it appears.

That means a current-year salary has to beat the indexed version of your older earnings, not just the original dollar amount. When you check your earnings record on SSA's site, the indexed figures are what matter for this comparison.

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How to check your own numbers

The quickest way to see where you stand is to log into your My Social Security account at ssa.gov. Your earnings record shows every year of reported income, and your benefit estimate shows what you would receive at different claiming ages based on your current history.

Start by counting your working years. If you have fewer than 35, any year with real earnings will help because you are replacing zeros.

If you already have 35 or more, find the lowest year in your top 35 and compare it to what you expect to earn by working longer. If the new year were higher, the difference divided by 420 gives you a rough idea of how much your monthly average could increase.

For a more precise look, the SSA also has an online calculator that lets you enter hypothetical future earnings and see how they would affect your projected benefit.

If you're already collecting benefits

For retirees under full retirement age (FRA) who are already receiving Social Security, earning above $24,480 in 2026 triggers a temporary withholding of $1 in benefits for every $2 over the limit. Those withheld amounts are credited back once you reach full retirement age, so nothing is permanently lost, but the reduction does affect your check in the short term.

The SSA's Earnings Test Calculator can show how that interaction would play out for your specific income, which is worth running before making a decision about additional work.

Bottom line

Retiring is a big decision, and it is understandable to want more than a guess before you choose your timing. Your Social Security earnings record can provide at least part of that clarity. A quick look can show whether one more year of work is likely to raise your monthly benefit or leave it right where it is.

If that extra year would improve your record, the math may favor staying a little longer. If it would not, then your benefit is not the deciding factor, and the choice comes down to everything else that matters to you personally.

Either way, running that comparison takes only a few minutes at ssa.gov, and it's one of the simpler ways to make the right moves before locking in a decision that's hard to reverse.

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