The annual cost-of-living adjustment for Social Security benefits is based on how inflation is running in the third quarter. The formula reflects monthly changes for July, August and September for the Consumer Price Index for Urban Wage Earners and Clerical Workers.Social Security benefits would increase beginning with December benefits, which are payable January 2026. Federal Supplement Security Income payments would increase for January but those payments would be made at the end of December.This year, th ...