The SSDI program pays benefits to workers who have paid Social Security taxes, which is what makes it an insurance program. On the other hand, SSI is means-tested and available to people who have never paid into the system.
The SSDI and SSI programs are administered by the Social Security Administration (SSA). Only claimants who are unable to work because of a disability and meet medical criteria can qualify for benefits under either program.
Claimants may qualify for either program at any age, but a beneficiary of SSI is likely to have had a disability since birth or from a young age. Many SSI recipients are children (with payments based on their parents’ Social Security contributions) or are adults who have been disabled since childhood.
Beneficiaries of SSDI are typically older workers who have been injured or contracted a disease that has led to their disability.
In most cases, the medical requirements for receiving disability payments are the same under both programs and disability is determined by the same process.