In certain circumstances, you can collect SSI and SSDI at the same time (called "concurrent benefits"). This happens when a disability applicant is approved for Social Security Disability (abbreviated as SSD or SSDI) but receives only a low monthly payment. (A low SSDI payment can be caused by not working much in recent years or making low wages.)
To qualify for an SSI payment in addition to an SSDI payment, your unearned income must be less than $735 per month. The SSI income limits are fairly complicated, however; this limit is higher in some states, and if you are working and making some money, a different limit applies. (See our article on the SSI income limit for more information.) The SSI program also has asset limits.
If your income and assets are low enough to qualify for Supplemental Security Income (SSI), and you also worked long enough in a job that paid taxes into the Social Security system to qualify for Social Security disability insurance (SSDI), it's not unlikely you'll receive both types of benefits at once. (However, keep in mind your SSDI payment is included in calculating your eligibility for SSI. In many cases, your SSDI payment will be so high you won't qualify for SSI.)
You won't receive a higher monthly combined benefit than you would under the SSI program alone. Your SSI payment will be lowered by your SSDI payment to match the maximum SSI payment. If your SSDI benefit is under $735 per month (the current SSI monthly payment amount) and you qualify for SSI, you will receive an SSI payment. In other words, if your SSDI benefit is less than $735 per month, you can receive both SSI and SSDI benefits at once.
Whether you apply for SSI, SSDI (also called SSD), or both, the Social Security office will decide whether your claim is concurrent, depending on your income and assets. The category of your disability claim will make no difference as to how the claim is processed. In other words, an SSI claim will be handled in exactly the same way as an SSDI claim. The same definition of disability and the same disability evaluation process is used for both programs.
The benefit to collecting SSI when you are collecting a low monthly SSDI benefit is that the SSI payment will raise your benefit up to $735 per month.
The benefit to being able to collect SSDI when you are eligible for SSI is that you may be eligible to get on Medicare as an SSDI recipient (although you must wait two years from when your SSDI eligibility begins).
In contrast, SSI recipients are eligible for Medicaid alone. While Medicaid does provide payment for more services than Medicare, more doctors accept payments from Medicare, so it can be easier to find a provider. For more information, see our article on getting Medicare or Medicaid while on disability.