Tax guides built around the question you are actually asking
Twelve focused guides—one real problem per page. Use a worked example, inspect the formula, catch a common error, or compare two methods before opening the linked calculator.
Federal income
Worked example · formula · mistakes · comparison
2026 federal income tax worked example: from gross income to tax
Follow one single-filer example through adjustments, the standard deduction, three marginal brackets, and the final planning estimate.
Read the guide →Marginal vs effective tax rate: the difference a calculator should show
Understand why your top bracket, total tax divided by taxable income, and total tax divided by gross income answer different questions.
Read the guide →Gross income vs AGI vs taxable income: stop entering the wrong number
Map the three income layers to a federal tax calculator and see why using gross pay in every field can materially overstate tax.
Read the guide →Standard deduction vs itemized deductions: a comparison workflow
Compare the two deduction paths without simply adding them together or assuming the larger raw total is automatically allowable.
Read the guide →1099 & self-employment
Worked example · formula · mistakes · comparison
1099 tax worked example: revenue, expenses, SE tax, and reserve
Trace a freelancer estimate from $90,000 of receipts through business profit, self-employment tax, income-tax inputs, and quarterly cash planning.
Read the guide →Why self-employment tax uses 92.35% of net profit
Unpack the regular Schedule SE base, the Social Security and Medicare pieces, the wage-base interaction, and the employer-equivalent deduction.
Read the guide →1099 vs W-2 taxes: compare the same compensation honestly
Compare business profit with employee wages without ignoring employer payroll tax, benefits, expenses, withholding, or worker-classification rules.
Read the guide →Six quarterly-tax reserve mistakes freelancers can catch early
Avoid confusing a cash reserve, an equal quarterly budget, a current-year estimate, and the federal required annual payment.
Read the guide →Sales tax
Worked example · formula · mistakes · comparison
Sales tax worked example: price, combined rate, tax, and total
Calculate one transparent transaction and see which legal inputs—location, taxability, sourcing, date, and rounding—the arithmetic cannot determine.
Read the guide →Add sales tax vs reverse sales tax: two formulas, two different bases
See why multiplying a tax-inclusive total by the rate does not recover the included tax, with a $108.25 example.
Read the guide →Why a ZIP code can return the wrong sales tax rate
Understand postal geography, overlapping tax districts, sourcing, and address-level verification before collecting tax from a customer.
Read the guide →Sales tax rounding: line item vs invoice total
See how cent rounding and calculation level can create reconciliation differences, and why the jurisdiction's rule must control the point-of-sale setup.
Read the guide →