Retirees who spent a few years out of the workforce, whether raising children, changing careers, or dealing with illness, may be collecting a smaller Social Security check than they need to. The federal benefit formula averages a worker’s highest 35 years of wage-indexed earnings and divides by 420 months to set the monthly payment. When someone has fewer than 35 years of recorded wages, the formula fills the gap with zeros, dragging down the average and shrinking the benefit. One additional year of earnings can knock out a zero, raise the average, and permanently increase the monthly check.
How the 35-year averaging window shapes every monthly check
The Social Security Administration calculates what it calls the Average Indexed Monthly Earnings, or AIME, by selecting a retiree’s highest 35 years of wage-indexed earnings and dividing the total by 420 months. For a person reaching age 62 in 2025, those highest 35 years of indexed earnings form the entire basis of the benefit calculation. The statutory authority for this system sits in the Social Security Act, codified at 42 U.S.C. 415, which defines computation base years, wage indexing tied to the National Average Wage Index, and the selection mechanics for benefit computation years.
The practical consequence is straightforward. A worker with 30 years of earnings and five years of zeros has those five blank years averaged into the denominator. Each zero year pulls the AIME down, and because the Primary Insurance Amount, or PIA, is derived directly from the AIME, the monthly benefit drops accordingly. A nonpartisan Congressional Research Service analysis confirmed that when base years are fewer than 35, years of no earnings are used, meaning zeros enter the formula automatically.
How SSA recalculates benefits after a new year of wages
The benefit is not permanently locked the moment someone files. Each year, SSA reviews beneficiaries’ reported wages. If the latest year of earnings ranks among a retiree’s highest 35, the agency recalculates the benefit and pays any increase retroactive to January of the year after those earnings were recorded. The recalculation happens without the beneficiary filing a request.
Federal regulation reinforces this process. Under 20 CFR section 404.280, SSA may recompute the PIA after entitlement and generally does so only when the recalculation would increase the benefit. That one-directional design means a retiree who works an additional year faces no risk of a lower payment from the recomputation itself.
The effect of replacing a zero is not uniform across earners. When a zero year is swapped for a year of wages at or above the national average, the jump in AIME is larger than when a low-wage year replaces that same zero. The bend points in the PIA formula also matter: because the formula replaces a higher share of the first slice of AIME and a smaller share of higher slices, an extra year of earnings can have a proportionally bigger impact for some mid-range earners than for very high earners whose AIME is already well above the upper bend point.
Who stands to gain the most from working longer
Retirees with long career breaks are often the ones who benefit most from an extra year or two of work. Someone who spent a decade out of the labor force caring for family members may have 25 years of earnings and 10 years of zeros in the calculation. Each additional year of work in their 60s replaces one of those zeros until they reach 35 years of covered earnings. For them, continuing part-time work can yield a permanent benefit increase that lasts for the rest of their lives.
By contrast, a worker who already has more than 35 years of earnings may still see an increase, but only if the new year of wages is higher, after indexing, than one of the lower years currently in the 35-year set. In that case, the new year bumps out a low-earning year rather than a zero. The gain is real but typically smaller than the jump from replacing a zero.
Checking your own record and potential increase
Retirees and near-retirees can estimate the value of another working year by reviewing their earnings history. SSA’s online tools allow beneficiaries to see which years have no covered earnings and which years show relatively low wages. Comparing a projected year of work to those low or zero years gives a sense of how much the AIME might rise if the new year enters the top 35.
Internal agency guidance in the Program Operations Manual System explains how technicians apply these rules in day-to-day cases. The section on recomputation of benefits details when a new computation year is added, how the 35-year window is updated, and how any resulting increase is credited to the beneficiary’s record.
For retirees who can still work and who see multiple zeros or very low earnings years on their statement, the message is clear: even limited additional earnings can have a lasting payoff. By understanding how the 35-year averaging window operates and how SSA automatically recalculates benefits, workers and retirees can make better-informed decisions about whether another year on the job is worth it for their long-term retirement income.
Free tool for readers: Not sure whether your own retirement is on track? You can check your free Retirement Safety Score — a 0–100 number plus a few personalized steps — in about five minutes, with no sign-up required to see your score.
