SSDI (Social Security Disability Insurance) is for people who have worked and paid Social Security taxes. SSDI benefits are based on your earnings record, and if found disabled, you automatically qualify for Medicare after a waiting period. SSI (Supplemental Security Income) is for people with little income and few assets, even if they haven’t worked much. SSI is based on your financial situation, and you will often qualify for Medicaid if found disabled. There are strict income and asset limits to qualify for SSI.