Self-employment tax is a tax consisting of Social Security and Medicare taxes primarily for individuals who work for themselves.

It is similar to the Social Security and Medicare taxes withheld from the pay of most wage earners.
You figure self-employment tax (SE tax) yourself using Schedule SE (Form 1040). Social Security and Medicare taxes of most wage earners are figured by their employers.

Also you can deduct the employer-equivalent portion of your SE tax in figuring your adjusted gross income. Wage earners cannot deduct Social Security and Medicare taxes.