SCorpMath is a free educational tax calculator toolkit for U.S. self-employed business owners, freelancers, 1099 contractors, and LLC owners. It helps users estimate rough self-employment tax and S-Corp payroll tax differences before discussing assumptions with a qualified tax professional. It includes S-Corp, Schedule C vs S-Corp, self-employment tax, 1099 vs W-2, and reasonable salary worksheet pages. It is not tax, legal, accounting, payroll, or financial advice.