Business tax / Free financial tools

C Corporation Income Tax Calculator

Estimate ordinary federal C corporation tax from book profit, tax adjustments and usable losses.

US federal • 2026 · Instant results · No sign-up

Enable JavaScript to use this interactive calculator. The calculation method and assumptions are explained below.

How this calculator works

Taxable profit = book profit + add-backs − additional deductions − usable losses, floored at zero. Ordinary federal C corporation tax is modeled at 21%. Book profit after tax uses the original book profit, not adjusted taxable profit.

Planning estimate only. Review the assumptions alongside the result before using it for a tax, financing or business decision.

IRS Form 1120 instructions

Common questions

Is this suitable for an S corporation or LLC?

Not automatically. S corporations and many LLCs pass income through to owners. Legal entity type and tax classification are different questions.

Can I deduct every prior-year loss?

No. Enter only the amount usable under the relevant loss rules and limitations. Credits, corporate AMT and international provisions are excluded.

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