"Gainful work activity” is Social Security's term for work you do for pay or profit. Employment that provides income above a certain level is considered “substantial gainful activity,” or SGA, and renders you ineligible for Social Security Disability Insurance (SSDI).
The SGA limit is adjusted annually to reflect changes in national average wages. In 2023, it's $1,470 a month ($2,460 for blind people). If you make more than that, your application for SSDI benefits will be denied. If you already are receiving benefits, you'll lose them in most circumstances if your income rises above the cap.
The strict limits grow out of the core purpose of Social Security disability benefits: to provide financial support to people temporarily or permanently unable to work because of a medical condition. You are allowed to do some paying work while drawing disability benefits. But if you are able to do “substantial” work, the reasoning goes, you are not, by definition, disabled.
The substantial gainful activity test applies to all applicants for SSDI as well as ongoing recipients of SSDI. For Supplemental Security Income (SSI), the other Social Security-administered benefit for people with disabilities, it comes into play only at the filing stage.
That means you can be denied SSI if your work income exceeds the SGA limit when you file for benefits. But the substantial gainful activity limit does not apply once you are getting SSI, although you will be subject to separate, SSI-specific limits on income. People who get SSI on the basis of blindness are exempt from income limits, and the substantial gainful activity limit does not apply to them at any point.
For wage earners, SGA is measured in gross pay. If you are self-employed, Social Security applies net income to the cap but may weigh other measures of work activity to determine if your gainful activity is substantial. For example, it might consider the number of hours you put into managing your business or whether your professional activity is comparable, in terms of time, skills and duties, to that of nondisabled people doing the same type of work.