Corporate income tax in the United States is levied at a flat federal rate of 21% on taxable income since the Tax Cuts and Jobs Act of 2017, down from a graduated structure that peaked at 35%. However, the effective tax rate most corporations actually pay is significantly lower — S&P 500 companies average an effective rate of 15-18% due to deductions, credits, depreciation schedules, and international tax planning strategies. State corporate taxes add 0-12% depending on jurisdiction (with Nevada, Wyoming, and South Dakota imposing no corporate income tax), bringing combined federal-state rates to 21-33%. Our corporate tax calculator computes federal tax liability, applies state tax rates, accounts for common deductions (depreciation, business expenses, net operating loss carryforwards), and calculates the effective tax rate — the percentage of pre-tax income actually paid in taxes — helping business owners and financial analysts understand the true tax burden on corporate earnings.
Federal corporate tax after the TCJA
The 2017 Tax Cuts and Jobs Act replaced the graduated corporate rate structure (15% on first $50K, 25% on $50K-$75K, 34% on $75K-$10M, 35% above $10M) with a flat 21% rate, simplifying calculations but eliminating the lower rates that benefited small corporations. A corporation with $500,000 taxable income now pays $105,000 in federal tax regardless of size. The TCJA also introduced the 20% Section 199A deduction for qualified business income from pass-through entities (S-corps, LLCs, partnerships), effectively reducing the top individual rate on business income to 29.6% — still higher than the 21% corporate rate but with only one layer of tax versus the double taxation of C-corps (corporate tax plus dividend tax on distributions).
State corporate tax variations
State corporate income tax rates range from 0% (Nevada, Ohio, South Dakota, Texas, Washington, Wyoming — though some impose gross receipts or franchise taxes instead) to 11.5% (New Jersey). California charges 8.84%, New York 7.25% (with a 0.15% MTA surcharge for NYC-area businesses), and Illinois 9.5% (including the personal property replacement tax). State taxes are deductible against federal taxable income, so a 7% state rate effectively costs approximately 5.5% after the federal deduction. Nexus rules determine which states can tax a corporation — historically based on physical presence, but the Wayfair decision (2018) expanded nexus to include economic presence, meaning online businesses may owe tax in states where they have significant sales even without employees or offices.
Reducing effective corporate tax rate
Legal strategies to reduce effective tax rate include accelerated depreciation (Section 179 allows immediate expensing of up to $1,220,000 in qualifying equipment in 2026), bonus depreciation (100% first-year deduction for qualifying assets through 2026), research and development tax credits (up to 20% of qualified research expenses), and net operating loss (NOL) carryforwards (losses can offset up to 80% of taxable income in future years indefinitely). International tax planning through transfer pricing and foreign tax credits can further reduce effective rates for multinational corporations. Small businesses should evaluate whether C-corp or pass-through entity status produces lower total tax — the answer depends on whether profits are distributed (double-taxed as dividends from C-corps) or retained for growth (taxed at only 21% in a C-corp versus up to 37% through a pass-through).