If you believe you qualify for Social Security disability benefits, then it may make the most sense for you to apply for both SSDI and SSI.

You may get denied SSDI if you are not “insured” (see below) or if it’s been too long since you stopped working full time. Even if you get denied SSDI, you may still have an SSI claim.

You may be denied SSI if your household has too much in assets/income/resources. There are many rules about how these figures are calculated, so if you do get denied, make sure you understand why. Even if you get denied SSI, you may still have an SSDI claim.

Some people have both an SSDI and SSI claim, and the only issue is whether they are disabled. A person can be eligible for BOTH SSDI and SSI if their SSDI rate is low.

The SSA usually decides your eligibility for SSDI and/or SSI at the beginning of your claim by determining your “date last insured” for SSDI (and whether you are claiming to have become disabled on or before that date) and your SSI financial eligibility (assets/income/resources in your household). You can get denied one or both of those benefits before the SSA even gets to your medical conditions.

You can find more information here: https://www.ssa.gov/redbook/eng/overview-disability.htm