Every fall, one number quietly resets what more than 70 million Social Security and Supplemental Security Income checks will look like come January, and this year’s version now has a locked release date sitting one month out. The Social Security Administration is set to publish the 2027 cost-of-living adjustment on October 14, once the Bureau of Labor Statistics finishes counting September prices. AARP’s own economists, working from data through August, currently peg that adjustment at 3.6 percent — an estimate the group has already revised upward once this summer and could still move again before the government’s official number replaces it.
The Third-Quarter Price Count That Decides the Number
Social Security’s annual raise isn’t set by Congress or by the President; it’s produced by a fixed formula written into the Social Security Act in 1973. Each year’s COLA compares the average Consumer Price Index for Urban Wage Earners and Clerical Workers, or CPI-W, across July, August and September to the same three months from the last year a COLA took effect. Once the Bureau of Labor Statistics publishes the September reading, the calculation is arithmetic, not judgment — which is why October 14, the date the September inflation report itself comes out, doubles as the day the Social Security Administration releases the finished percentage.
The agency’s own table for this year’s calculation shows exactly how mechanical the process is: the third-quarter 2024 CPI-W averaged 308.729, the third-quarter 2025 average came in at 317.265, and the percentage difference between those two figures — 2.8 percent, rounded to the nearest tenth — became the raise now on retirees’ checks. The 2027 calculation will run the identical process, swapping in third-quarter 2026 data against the third-quarter 2025 base once September’s numbers exist.
That mechanism is public record. The agency’s own explanation of the formula, current through the 2026 adjustment, shows the math behind this year’s number: a 2.8 percent increase, calculated from the same third-quarter comparison, that took effect with December 2025 benefits paid out in January 2026. Two of the three months in the 2027 comparison — July and August — are already final. September is the one missing input, and it’s also the reason no organization, AARP included, can publish more than an estimate until the government’s own count lands.
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AARP’s Projection Moved From 3.5 to 3.6 Percent in a Month
AARP has been running its own COLA projection since mid-summer, updating it as each new inflation report arrives. As of its prior estimate, the figure stood at 3.5 percent; after the Bureau of Labor Statistics’ August reading came in slightly hotter than economists had expected, AARP’s updated forecast moved to 3.6 percent. That half-point of movement in a single month is itself a reminder of how much weight the final, unreleased September number carries.
The distinction between that number and an official COLA matters. AARP’s figure is built from two of the three months the government will eventually use, plus its own read on where September is likely to land — a projection, not a finding. Nothing about it binds the Social Security Administration, and the agency’s own calculation, due October 14, is free to land above or below it.
Last Year’s 2.8 Percent, the Benchmark for This One
The comparison point for any 2027 estimate is last year’s real number. Social Security benefits and SSI payments rose 2.8 percent starting with December 2025 benefits, paid in January 2026 — a figure the Social Security Administration’s own cost-of-living page still lists as the latest confirmed adjustment. AARP’s 3.6 percent projection, if it held through October, would run nearly a full point above that.
AARP also estimates the average monthly retirement benefit at about $2,086 as of July 2026. Applying a 3.6 percent increase to that baseline works out to roughly $75 more a month — arithmetic AARP performs in its own preview, not a figure the Social Security Administration has confirmed or will confirm before October 14. Multiplied across the tens of millions of retired workers who draw a monthly check, that arithmetic is why the October release draws more attention than almost any other single government data point on the calendar.
A Payment-Timing Detail Inside the Same Formula
Payment timing carries its own quirk that has nothing to do with the size of the raise. The Social Security Administration’s cost-of-living page notes that federal SSI payments are dated the first of the month, and because January 1 falls on a holiday, the January SSI payment is issued at the end of the preceding December instead. That detail applies every year the calendar lines up that way, regardless of whether the adjustment underneath it is 2.8 percent or 3.6 percent, and it is a separate fact from the COLA percentage itself.
Between Now and October 14, the Number Can Still Move
Nothing about the 2027 figure is final. The Bureau of Labor Statistics still has to publish the September Consumer Price Index, the Social Security Administration still has to run its own calculation against that data, and the resulting percentage — whatever it turns out to be — becomes official only when the agency posts it on October 14. AARP’s own preview is explicit that its 3.6 percent estimate is subject to change once the last month of data arrives.
For now, the only adjustment either source has confirmed as final is last year’s: 2.8 percent, effective with the January 2026 payment and documented on the Social Security Administration’s own cost-of-living page. Everything above that number, through October 14, remains AARP’s estimate to revise.
When the Deposit Amount Changes, Mistakes Can Follow
A COLA year means Social Security’s payment systems update the deposit amount on every account at once, and that kind of system-wide change is exactly when a payment can land late, arrive short, or trigger an overpayment notice that contradicts the new total. None of that depends on whether the final 2027 adjustment matches AARP’s 3.6 percent estimate or lands somewhere else — the mechanics of a changed deposit are the same regardless of the percentage.
The Social Security Check Protection Kit is an 18-page resource built around the 2026 payment calendar, a first-24-hours plan for a late or missing payment, and the three SSA forms that can stop or pause collection on an overpayment notice — SSA-561, SSA-632, and SSA-634.
See the payment calendar and the overpayment forms in The Social Security Check Protection Kit.
AI-assisted research and drafting; reviewed by an editor.
