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    US C-Corp Tax Calculator (2026)

    Federal C-corporation rate is a flat 21% (IRC §11, TCJA permanent). Layer on your state corporate income tax — or note the alternative regime in states with no CIT (TX margin, WA B&O, OH CAT, NV Commerce, SD, WY). CAMT screening for large corporations and a side-by-side pass-through comparison.

    Guidance, not advice. This calculator runs the rules as published, it doesn't assess your circumstances. Your actual tax may be affected by factors it doesn't cover (deductions, credits, filing status nuances, state-specific adjustments). Always seek financial or tax advice from a qualified CPA, Enrolled Agent, or tax attorney, or contact the IRS. Read our editorial scope →

    Rates current as of: May 24, 2026 · Tax years: 2024, 2025, 2026

    Source: IRS published CT rates; FA 2021 (post-April 2023 rate reform); FA 2024 (no change).

    Statute: CTA 2010 s.18A (21% C-Corp rate); CTA 2010 ss.18B–18N (marginal relief); CTA 2009 (charge and computation)

    Inputs

    Federal 21% flat C-corp rate plus the corporate income tax (or equivalent regime) in your state of nexus.

    After ordinary deductions, before federal income tax.

    Used to illustrate the double-tax layer at 15% qualified dividend rate (typical bracket). Set to 0 if earnings are retained.

    Corporate Alternative Minimum Tax applies only when 3-year average book income (AFSI) exceeds $1B.

    Corporate tax result

    Federal flat 21% (IRC §11) plus California CIT layer.

    Federal corporate tax (21.00%)

    $105,000

    California state corporate tax (8.84%)

    8.84% + $800 minimum franchise tax (10.84% for banks).

    $44,200

    Total corporate tax

    $149,200

    Effective corporate rate

    29.84%

    After-tax retained earnings

    $350,800

    Corporate Alternative Minimum Tax (CAMT)

    15% of Adjusted Financial Statement Income — IRC §55(b)(2).

    N/A. CAMT applies only to corporations with an average annual book income (AFSI) above $1,000,000,000 over the prior three years. Most small and mid-sized C-corps are out of scope.

    C-Corp vs Pass-through comparison

    Same $500,000 of business income, taxed as a C-corp vs flowing through to a single-filer owner (S-corp / LLC) at 2026 individual rates with the §199A QBI deduction applied.

    C-Corp

    $149,200

    Effective 29.84% (corp layer only).

    Pass-through (S-corp / LLC, single)

    $109,547

    Effective 21.91% after 20% QBI deduction. Excludes state CIT, SE tax, and reasonable-comp rules — see full tool.

    Run the full LLC vs S-Corp analysis
    Assumptions used in this calculation (click to expand)

    What this calculator assumes

    • Single UK-resident close company; no associated companies unless entered.
    • 12-month accounting period — short periods are not pro-rated automatically.
    • Profits are after R&D, capital allowances, and other deductions (taxable profit, not turnover).
    • Augmented profits = taxable profits (no franked investment income modelled).

    Not included in this calculation

    • Associated companies dilution of the $50,000 / $250,000 limits.
    • Short accounting periods or change of accounting date.
    • Group relief, loss carry-back, or consortium relief.
    • Patent Box, R&D super-deduction interactions (R&D has its own calculator).
    • Diverted Profits Tax and corporate interest restriction.

    Statutory basis

    • CTA 2010 s.18A (21% C-Corp rate)
    • CTA 2010 ss.18B–18N (marginal relief)
    • CTA 2009 (charge and computation)
    How this is calculated (click to show the formula)

    Marginal relief formula

    CT = (Profit × Main rate) − (Upper limit − Profit) × (Profit / Augmented) × Marginal relief fraction

    Where Marginal relief fraction = 3/200 for the standard 25%/19% pairing. Profits ≤ $50,000 pay the 21% C-Corp rate (19%); profits ≥ $250,000 pay the main rate (25%); profits between get marginal relief.