Updated February 28, 2019
In certain circumstances, you can collect SSI and SSDI at the same time (this is called receiving "concurrent benefits"). This happens when a disability applicant is approved for Social Security disability insurance benefits (abbreviated as SSDI) but receives only a low monthly payment. Someone usually gets a low SSDI payment if they made low wages or they did not work much in recent years.
To qualify for an SSI payment in addition to an SSDI payment, your unearned income (meaning SSDI) must be less than $771 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, some of that income doesn't count towards the limit. (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 to qualify for Social Security disability insurance (SSDI), it's not unlikely you'll receive both types of benefits at once. Just keep in mind that the amount of 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.
If your SSDI benefit and any other income is under $771 per month (the current SSI monthly payment amount) and you qualify for SSI, you will receive an SSI payment. For instance, if your SSDI payment is $500, and you have no other income, you would also receive a $271 SSI payment.
Some people are eligible for both SSDI and SSI for just a short time. Here's when that might happen. If you've been approved for SSDI but are within the five-month waiting period (before you receive any actual benefits), you won't get an SSDI payment, but you could get SSI payments if you have little countable income. After the five-month period, you would start receiving SSDI payments and your SSI payment would be adjusted. Your SSI payment will be lowered by your SSDI payment to match the maximum SSI payment. For instance, if you receive $771 in SSI for five months and then start to receive a $600 SSDI payment, your SSI payment would theoretically be reduced to $100 (but Social Security ignores $20 of unearned income, so your SSI payment would really only be reduced to $120).
Whether you apply for SSI, SSDI, or both, the Social Security office will decide whether your claim is for concurrent SSDI and SSI benefits, depending on your income and assets. The category of your disability claim will make no difference as to how the claim is processed at Disabiilty Determination Services (the state agency that determines when you are disabled). 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 $771 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. (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.