US Business Federal Income Tax Calculator
Sole prop · Partnership · S-Corp · C-Corp · QBI · Self-employment tax
Total tax at this profit level, by entity structure (same $ profit, same filing status/state)
Estimated quarterly payments — avoids an IRS underpayment penalty
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What Is a Business Federal Income Tax Calculator, and Why Use One?
Business owners in the US do not all pay tax the same way. A sole proprietor, an S-corp shareholder, and a C-corp all follow different rules, and the entity you choose changes how much you owe in ways that are easy to miss. This calculator lets you enter your net profit once and see the federal income tax, self-employment or payroll tax, and estimated state tax side by side.
In practice, three things drive your business tax bill: your entity type, your net profit, and your filing status. As a result, two businesses earning the same $150,000 can end up with noticeably different total tax simply because one is a sole proprietorship and the other elected S-corp status.
When you should recalculate
Because tax brackets, the QBI deduction thresholds, and Social Security wage caps adjust most years, it is worth rerunning the numbers whenever your profit changes meaningfully, you are weighing an entity election, or a new tax year begins. Use the Entity Compare tab above to see, in real numbers, how a different structure would change what you owe.
Tips for Getting the Most Out of This Calculator
Compare entities before you file an election
An S-corp election is not automatically better. It adds payroll costs, a separate tax return, and reasonable-compensation rules. Run your actual profit through the Entity Compare tab first, then weigh the tax savings against the added complexity.
Set a realistic S-corp salary
The IRS expects an S-corp owner's W-2 salary to reflect fair market pay for the work performed. Setting it artificially low to shrink payroll tax is one of the most common audit triggers, so treat the salary field as a real number, not a lever to minimize tax.
Don't ignore the QBI deduction
The Section 199A deduction can shield up to 20% of qualified business income from federal tax for sole proprietors, partnerships, and S-corps. It phases down above certain income thresholds, which this calculator models conservatively, so treat the QBI figure as a floor rather than a guaranteed ceiling.
Factor in self-employment tax separately from income tax
Self-employment tax covers Social Security and Medicare, and it applies on top of, not instead of, federal income tax. A profitable sole proprietorship can owe more in SE tax than in income tax at moderate income levels, so check both figures in the Breakdown tab.
Use the Quarterly Payments tab to avoid penalties
The IRS expects most business owners to pay estimated tax four times a year. Underpaying any quarter can trigger a penalty even if the full balance is paid by the April deadline, so treat the quarterly figures here as a minimum planning baseline.
Frequently Asked Questions
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Sources & Further Reading
Official IRS guidance on filing requirements, deductions, and recordkeeping for sole proprietors, partnerships, and corporations.
The official rules behind the QBI deduction modeled in this calculator, including the wage and property limitations.
Instructions and safe-harbor rules for pass-through business owners making quarterly estimated tax payments.
A plain-language overview of how business structure affects federal tax obligations, from the SBA's official guide.
Disclaimer
This calculator is provided for general informational and educational purposes only and does not constitute tax, legal, or financial advice. It is not affiliated with, endorsed by, or a substitute for consultation with the IRS, your state's department of revenue, or a licensed CPA, EA, or tax attorney.
All figures, including federal income tax, corporate tax, self-employment or payroll tax, the QBI deduction, and estimated quarterly payments, are approximations based on the numbers you enter and simplified versions of current IRS formulas. They do not account for the alternative minimum tax, the net investment income tax, multi-owner partnership or S-corp allocations, the full QBI wage and qualified-property limitation, or state franchise and margin taxes that may apply to your actual return.
Figures reflect IRS Rev. Proc. 2025-32 and the One Big Beautiful Bill Act (OBBBA, signed July 4, 2025) as currently understood and may change as further IRS guidance is issued. Always confirm your actual liability with a licensed CPA/EA and irs.gov/businesses before filing or making a tax payment.
FinToku is not a CPA firm, law firm, or tax preparer, and does not prepare or file returns on your behalf. Use of this tool does not create any advisory relationship between you and FinToku. You are solely responsible for decisions made using these estimates. See FinToku's full Financial Disclaimer for more detail.
Estimates only — not tax advice. Consult a CPA/EA before filing. FinToku