Schedule C's net profit arrives here and becomes 15.3% on 92.35% of it — the tax an employee never sees because an employer pays half. The wage base caps the Social Security half; Medicare has no ceiling at all.

Everything on this site that lands here

Each article declares the sheet its number ends up on, so this list is the writing itself rather than a summary of it.

ReadWhere it lands
$400 is not the line most people think it is the $400 net-earnings test
You can pay the whole bill and still owe a penalty paid across the year on Form 1040-ES
You can usually still go back three years refiled for past years on Form 1040-X
The notary exemption is narrower than your fee with the notary fee exclusion taken out
The gym calls you a contractor. Three questions decide whether that is true. or Form 8919, if the gym was really an employer

The official page

Everything here is written from the IRS's own material, and the place to check it is Schedule SE on irs.gov. Figures and rules change; the source is what settles them.

This is educational material, not tax advice. Your own situation may turn on facts this page does not know about.