Doing volunteer work can, in some circumstances, be considered substantial gainful activity, which could cause your Social Security disability benefits to terminate. (See 20 CFR 404.l565). Substantial work activity is work activity that involves doing significant physical or mental activities. Your work may be substantial even if it is done on a part-time basis or if you do less, get paid less, or have less responsibility than when you worked before. Gainful work activity is considered gainful whether or not a profit is realized, especially if the work is a type of work usually done for pay or profit. (See 20 CFR 404.1572).