It is easy to just lump the two critical forms of financial support offered by the Social Security Administration -- Social Security Disability Insurance (SSDI) and Supplemental Security Income (SSI) -- together. But these are two distinct forms of financial support with different functions and different qualifications.
Social Security Disability Insurance is a system that someone "pays into." You must have at least 20 quarters of coverage over the last 10 years in order to qualify for SSDI, in addition to having a substantiated disability that has lasted for at least 12 months. There are other guidelines and rules for SSDI benefits, but these are the basic ones.
For Supplemental Security Income, however, the basic rules are quite different. SSI has no work history requirement, so people denied for SSDI due to not meeting the work history requirement could apply for SSI. However, SSI is meant for those with limited financial means who also have a disability or are 65 years old or older. SSI is also pro-rated based on the financial means of the applicant, a significant difference from SSDI.
These two forms of support offered by the Social Security Administration are crucial, but the ways to get approved for them differ. Anyone who is entering into discussions with the SSA in an effort to secure either form of financial support should consult with an attorney as soon as possible to get the ball rolling.
Source: FindLaw, "What is the Difference Between SSDI and SSI?," Accessed March 31, 2017