What is a Lump-Sum Social Security payment?
A lump-sum Social Security payment is a payment that includes benefits for one or more earlier year(s).
This is different from lump-sum death benefits. No part of a lump-sum death benefit is taxed, so you don't need to report it here.
For example:
If you applied for Social Security disability benefits in 2024 and were told that you were ineligible, but you had appealed the decision and won, then in 2025 you would receive a lump-sum payment for the past Social Security benefits.