The IRS corporate tax rate is a flat 21% on the taxable income of every C-corporation, set permanently by the Tax Cuts and Jobs Act of 2017.1Office of the Law Revision Counsel. 26 USC 11 – Tax Imposed There are no brackets. A corporation with $50,000 of taxable income pays the same percentage as one with $50 billion. The full tax bill, though, often includes more than that one calculation.
Who Actually Pays the 21% Rate
The 21% rate applies to C-corporations, meaning entities taxed under Subchapter C of the Internal Revenue Code. A C-corporation is a separate taxpayer that files its own Form 1120 and pays tax on its own profits.2Internal Revenue Service. Forming a Corporation When those after-tax profits are distributed as dividends, shareholders owe tax again at their individual rates. That double layer is the defining tradeoff of the C-corporation structure.
S-corporations, partnerships, and sole proprietorships are never subject to the 21% corporate rate. Their income passes through to the owners’ personal returns and is taxed there instead. To be an S-corporation, a business must file Form 2553, keep to 100 or fewer shareholders, issue only one class of stock, and meet other eligibility rules.3Internal Revenue Service. S Corporations If you run one of these pass-through entities, the 21% figure is not your rate.
What the 21% Is Applied To
The rate hits taxable income, not gross revenue. Taxable income is what’s left after a corporation subtracts all allowable deductions from its gross income.4Office of the Law Revision Counsel. 26 USC 63 – Taxable Income Defined Gross income covers sales, service fees, investment returns, rents, and royalties. Deductions do most of the work of shrinking that number.
Ordinary Business Deductions
Corporations deduct ordinary and necessary expenses: employee compensation, rent, supplies, insurance, advertising, and travel.5Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses Capital expenses such as equipment and buildings are recovered over time through depreciation rather than deducted immediately. Interest on business debt is deductible only up to 30% of the corporation’s adjusted taxable income for the year, and any disallowed interest carries forward.6Internal Revenue Service. Questions and Answers About the Limitation on the Deduction for Business Interest Expense
Net Operating Losses
When deductions exceed income, the resulting net operating loss carries forward indefinitely. In any future year, the deduction is capped at 80% of that year’s taxable income.7Internal Revenue Service. Tax Cuts and Jobs Act – A Comparison for Businesses So a corporation with large stored losses still owes some tax in its first profitable year.
Charitable Contributions
For tax years beginning in 2026, a corporation can deduct charitable contributions only to the extent they exceed 1% of taxable income, and only up to 10% of taxable income.8Office of the Law Revision Counsel. 26 US Code 170 – Charitable, Etc., Contributions and Gifts The 1% floor means the first slice of donations produces no tax benefit. A corporation with $5 million in taxable income gets nothing back on its first $50,000 of giving. Contributions above the 10% ceiling carry forward for up to five years.
Extra Federal Taxes That May Apply
The Corporate Alternative Minimum Tax
Since 2023, the largest corporations run a second calculation. The corporate alternative minimum tax imposes a 15% rate on adjusted financial statement income, essentially the profit reported to shareholders with certain adjustments. It applies only if a corporation’s average annual adjusted financial statement income over three years reaches at least $1 billion. If that 15% figure exceeds what would be owed under the regular 21% rate after credits and deductions, the corporation pays the higher amount. This reaches only a few hundred of the largest U.S. companies. If your business is not in that group, this provision does not affect you.
The 1% Stock Buyback Excise Tax
Publicly traded domestic corporations that buy back their own stock owe a 1% excise tax on the fair market value of shares repurchased during the year.9Office of the Law Revision Counsel. 26 US Code 4501 – Repurchase of Corporate Stock It applies only when total repurchases exceed $1 million for the year, and only to stock traded on an established securities market. Credits and deductions cannot reduce it. It has been in effect for repurchases after December 31, 2022.
Deadlines and Estimated Payments
Corporations pay tax throughout the year, not just at filing. Quarterly estimated payments are due on the 15th day of the 4th, 6th, 9th, and 12th months of the tax year.10Internal Revenue Service. Publication 509 (2026), Tax Calendars For a calendar-year corporation, that means April, June, September, and December. Each payment should cover roughly one quarter of the expected annual liability.
Form 1120 is due by the 15th day of the fourth month after the tax year ends, which is April 15 for calendar-year filers.11Internal Revenue Service. Instructions for Form 1120 (2025) Filing Form 7004 by that same date grants an automatic six-month extension to file, but not to pay. Tax owed is still due by the original deadline, and interest starts running immediately on anything unpaid.
Penalties for Late Filing and Underpayment
A late return triggers a failure-to-file penalty of 5% of the unpaid tax per month, up to 25%.12Internal Revenue Service. Failure to File Penalty If the return is more than 60 days late, the minimum penalty is $525 or 100% of the unpaid tax, whichever is less. A separate failure-to-pay penalty of 0.5% per month runs alongside it, also capped at 25%. When both apply in the same month, the filing penalty is reduced by the payment penalty so the combined rate stays at 5% per month.
Underpaying quarterly estimates draws interest rather than a flat penalty. For the first quarter of 2026, the underpayment interest rate is 7% for most corporations and 9% for large corporate underpayments exceeding $100,000.13Internal Revenue Service. Quarterly Interest Rates These rates reset quarterly based on the federal short-term rate.
State Corporate Taxes on Top
The 21% federal rate is only part of the bill. Forty-four states and the District of Columbia impose their own corporate income tax, with top rates roughly between 2.5% and 12%. A few states impose no corporate income tax but may charge alternatives.
Some states use gross receipts taxes, franchise taxes, or capital stock taxes in place of or alongside an income tax. Because these are calculated on revenue, net worth, or another base, a corporation can owe state tax in a year with no profit at all. A corporation’s real effective rate depends on where it operates and how its income is sourced across jurisdictions.