You must be between the ages of 18 and 65 years old to be eligible for Social Security Disability Insurance (SSDI). For Supplemental Security Income (SSI) on the other hand, you can be between birth and 65 years old. Once an individual has attained full retirement age, they will begin receiving their regular retirement benefits.
If you worked long enough and have paid Social Security taxes, the SSDI program will pay benefits to you as well as certain family members. An adult child may qualify for benefits on your earnings record if he or she has a disability that started before the age of 22.
The SSI program, on the other hand, pays benefits to adults who are disabled and children who have limited income and resources.