You are self-employed if you carry on a trade or business as a sole proprietor, are an independent contractor, are a member of a partnership, or are in business for yourself in any other way.

Self-employment can include work in addition to your regular full-time business activities, such as certain part-time work you do at home or in addition to your regular job.

This information is found in the Filing Information chapter of Publication 17, Your Federal Income Tax.