When your FICA is withheld you are buying three things. They are a retirement plan, a survivor’s benefit plan and a disability benefit plan. The more you pay in, the higher your benefit rate. So, if you have worked enough, then you file for the SSDI program. Now, if you never worked and have resources so limited that you are eligible for public aide, then the SSI program is what you file for if you are disabled.
Check the upper left hand corner of any correspondence from the SSA. That will give you an idea of which program is contacting you. SSDI stands for Social Security Disability Insurance and you will see “Retirement, Survivors and Disability Insurance” in the heading under the Social Security Administration. For the SSI you will see the term Supplemental Security Income in the heading. Make a practice of keeping everything the SSA sends you and a copy of everything you send them.