What is the difference between SSI and SSDI?

The main difference between SSI and SSDI is simply that SSI has nothing to do with work history and SSDI does. SSI stands for Supplemental Security Income and applies to applicants on a needs-based system according to possessions and income and not work history. Applicants who have worked may apply for SSI as well. SSDI, on the other hand, is a result of the applicant's taxes paid. Taxes paid means that the applicant has worked a certain number of years and therefore has contributed to Social Security taxes. If the applicant is found to qualify for SSDI, the family members of the applicant may receive a fraction of those benefits as well called auxiliary benefits. In some cases, applicants may qualify for both SSI and SSDI. Watch a video on SSI vs. SSDI.