Many people assume that those who receive Social Security disability benefits from the Social Security Administration are forbidden from working. As this thought process goes, if the person is disabled and is thus unable to work, then their SSDI benefits compensate them for the work they can't do or perform. As such, they aren't allowed to work, even if they could.
But this line of thinking is actually incorrect. People who live with disabilities and receive Social Security disability benefits are allowed to work so long as they don't earn enough to break a threshold known as "substantial gainful activity," or SGA. Substantial gainful activity is defined as earning more than a certain amount every month ($1,130 per month, or $1,820 if you are blind). If you cross that threshold, then you are not allowed to work while receiving SSDI benefits.
Beyond this SGA aspect, there are three ways to maneuver your way around the Social Security Administration's rules regarding SGA. First, there is a trial work period that you can engage in. This is when someone tests their abilities at work following a disability. Your trial work period constitutes nine months in a 60-month period. If you earn at least $810 and/or if you work more than 80 hours in a month as a self-employed individual, then that month counts as one of your nine months during the trial work period. During these nine months, you can earn as much as you want and still receive Social Security disability benefits.
There are two other options for you. You can extend your period of eligibility after the trial work period ends (an additional 36 months) where you receive SSDI benefits so long as you remain under the SGA threshold; and you can deduct expenses related to your disability from your monthly income, which could allow you to earn more than the SGA and still receive benefits.
Source: Motley Fool, "Can You Work While Receiving Social Security Disability?," Maurie Backman, May 16, 2016