Frequently Asked Questions
Common questions about our calculators, methodology, and policies.
Are these calculators free to use?
Yes. Every calculator on CentCalc is 100% free with no sign-up, no paywall, and no trial period. We are supported by display advertising (Google AdSense).
Do you collect my personal financial data?
No. Calculator inputs (salary, debts, savings, etc.) are processed entirely in your browser via JavaScript. They are never transmitted to our servers. See our Privacy Policy for full details.
How accurate are the calculations?
Formulas are 100% accurate against published sources (IRS Publications, SSA.gov, etc.). However, our models are simplified — they assume standard deduction (no itemizing), top marginal state rates in many cases, and no individual credits. Real-world tax owed may differ materially. Always verify with tax preparation software or a CPA before filing.
What tax year is the data current for?
Federal tax brackets, standard deductions, and FICA rates are current for tax year 2024 (IRS Revenue Procedure 2023-34). State tax rates are current as of Q1 2024. We update annually each Q4 after IRS publishes new inflation adjustments.
Why does my actual paycheck differ from the calculator?
Common reasons: (1) Your employer withholds based on your W-4 which may include extra withholding or exemptions; (2) You have pre-tax deductions (401k, HSA, FSA, health insurance) not modeled here; (3) State tax may include local taxes (NYC, Ohio cities, Maryland counties) we don't add; (4) Year-end bonus or commission withholding uses different rules.
Are calculators AdSense / SEO optimized or actually accurate?
We prioritize accuracy. Our editorial policy prohibits adjusting calculator outputs to favor advertisers or rank better in search. Every formula is hand-coded from authoritative sources by a human engineer, then peer-reviewed.
I found an error. What should I do?
Please use the 💬 feedback widget (bottom-right of any page) and include: (1) the calculator URL, (2) your exact inputs, (3) the result you got, (4) the result you expected, and (5) the authoritative source you compared against. We investigate every report within 7 business days.
Can I use these calculators for my business / clients?
You may use calculators for personal, non-commercial purposes. If you are a tax preparer, financial advisor, or other professional serving clients, please link them to our site directly rather than embedding outputs in client deliverables. For embedding / API licensing, contact us.
Do you cover non-US tax systems?
Currently all tax calculators are US-only (federal + all 50 states + DC). We may add Canada, UK, Australia in the future based on user demand.
Are you affiliated with any financial product companies?
No. We do not receive payment to recommend specific banks, insurance companies, brokerages, or tax software. Advertisers do not influence calculator content. See our editorial policy for full independence details.
Have a question we didn't answer?
Use the 💬 feedback widget at the bottom-right of any page, or contact us.