I believe this MarketWatch article about self-employment taxes -- for Social Security and Medicare -- could have a better title. Like the article says, the full-time self-employed are well aware of said tax. The article's purpose seems to be to inform readers -- especially those self-employed part-time or who do occasional work -- whether or not they are subject to said taxes. A title such as 'Is Work Income Subject To Social Security & Medicare Taxes?' better fits that purpose.
Some more specific kinds of work that the article doesn't mention are:
- Driving for Uber or Lyft is subject to self-employment taxes. The state of California government based on Assembly Bill 5 tried to turn said drivers into Uber or Lyft employees instead of independent contractors. This attempt was defeated by Proposition 22 this month (link). If treated as employees, they would pay half and their employers pay the other half of Social Security and Medicare taxes.
- Income to poll workers (for voting) and door-to-door census workers presumably are not subject to Social Security and Medicare taxes, since the work does not qualify as a "regular trade or business."
This Motley Fool article implies that Social Security and Medicare taxes are owed on all gig work. “Gig work” is not defined, but there can be exceptions if the work does not qualify as a "regular trade or business."
When filing taxes, self-employment income is reported on Schedule C and line 3 of Form 1040 Schedule 1. Income to poll workers (for voting), to door-to-door census workers, and for jury duty are reported on line 8 of Schedule 1 and not on Schedule C. The Form 1040 Instructions, page 82 show more kinds of income that go on line 8. Many are non-work income.