US Corporate Income Tax 2026: Rates, Rules & Deadlines

The federal corporate income tax rate is a flat 21% of taxable income (IRC §11). A calendar-year C corporation files Form 1120 by the 15th day of the 4th month after year-end, which is April 15. A six-month extension through Form 7004 pushes the filing date to October 15, but it does not extend the time to pay. Corporations that expect to owe $500 or more must also pay estimated tax in four installments (April 15, June 15, September 15 and December 15 for calendar-year filers). States add their own taxes on top.

Last verified: October 14, 2026. Federal and state tax rates, filing deadlines, deductions, credits and compliance rules may change. Confirm all requirements against the latest IRS instructions, enacted federal tax law, and the relevant state tax authority before filing. This guide is general information, not tax or legal advice.

Tax Year 2026 vs Returns Filed in 2026

This is the part most articles skip, and it causes real mistakes.

• Tax year 2026: the income your corporation earns during its 2026 tax year. For a calendar-year company, that is January 1 to December 31, 2026. You file that return in 2027.
• Returns filed in 2026: usually returns for tax year 2025.
• Estimated payments made in 2026: installments toward the 2026 tax year.

Why this matters today: if your calendar-year corporation extended its 2025 return, the extended due date is generally October 15, 2026, which is tomorrow. Publication 509 says Form 7004 gives an automatic six-month extension for Form 1120, and six months after April 15 lands on October 15.

The Federal Corporate Tax Rate in 2026

21% flat rate

Section 11(b) of the Internal Revenue Code says: "The amount of the tax imposed by subsection (a) shall be 21 percent of taxable income." You can read it on Cornell's Legal Information Institute. The Tax Cuts and Jobs Act set this flat rate for tax years beginning after December 31, 2017, and it still applies to tax year 2026.

There are no corporate brackets. A company with $50,000 of taxable income and one with $50 million both pay 21% at the federal level.

Worked example

A C corporation reports $500,000 of taxable income for 2026.

• Federal corporate income tax: $500,000 × 21% = $105,000

That is before credits, estimated payments already made, and state taxes.

The corporate rate vs the effective rate

Your statutory rate is 21%. Your effective rate is total tax divided by pre-tax profit. Deductions, credits and timing differences can make the effective rate lower. Accounting profit also differs from taxable income, so a company's financial statements and tax return rarely match.

How Corporate Taxable Income Is Calculated

The basic formula is simple:

Gross income − allowable deductions = taxable income

What counts as gross income

Sales revenue, interest, dividends, rents, royalties and gains from selling assets all generally count.

Common deductions

• Ordinary and necessary business expenses: wages, rent, utilities, supplies, advertising and professional fees.
• Depreciation and amortization: spreading the cost of long-lived assets over time.
• Interest expense: subject to limits (see below).
• Net operating losses (NOLs): losses from earlier years can reduce taxable income, subject to limits.
• Charitable contributions: deductible within limits.
• Dividends received deduction: a partial deduction for certain dividends received from other corporations.

For a beginner-friendly refresher on terms, see our tax terms glossary. To test a quick estimate, try our business income tax calculator guide and the income tax calculator.

Deductions vs credits

A deduction lowers taxable income. A credit lowers the tax itself, dollar for dollar. At a 21% rate, a $10,000 deduction saves about $2,100, while a $10,000 credit saves $10,000.

2025 law changes that affect 2026 planning

The IRS Form 1120 instructions note that P.L. 119-21, the One Big Beautiful Bill Act, changed several rules. Based on the IRS instructions and a law-firm summary:

• 100% bonus depreciation was reinstated on a permanent basis for qualifying property acquired after January 19, 2025 (Section 168(k)).
• Domestic research and experimental costs can be deducted again under new Section 174A, or capitalized and amortized over at least 60 months. This applies to amounts paid or incurred after December 31, 2024.
• The business interest limit under Section 163(j) returned to generally 30% of EBITDA for tax years beginning after 2024.

Worked example: a company buys $400,000 of qualifying equipment in 2026. With 100% bonus depreciation, it may deduct the full $400,000 in year one. At 21%, that deduction reduces federal tax by about $84,000 that year. Eligibility depends on the property and whether you elect out, so confirm with a tax professional.

Form 1120 and Who Must File

Who files

According to the Instructions for Form 1120, domestic corporations generally must file Form 1120, even with no taxable income, unless exempt under section 501. Some entities file special returns instead, such as Form 1120-S for S corporations.

Corporations must also e-file Form 1120 if they file 10 or more returns of any type during the calendar year (for returns filed on or after January 1, 2024). The IRS may waive this on written request in cases of hardship.

Which form for which entity

2026 Corporate Tax Deadlines

These dates apply to a calendar-year corporation. The rules in Publication 509 and the Form 1120 instructions work by month, and I calculated the dates from them.

Fiscal-year corporations

The rule is "the 15th day of the 4th month after the end of the tax year," so a fiscal-year company's dates shift. There is one special rule: Publication 509 says corporations with a fiscal year ending June 30 file by the 15th day of the 3rd month, and they use Form 7004 for an automatic 7-month extension.

Short tax years

Publication 509 also says corporations with a short tax year that began before January 1, 2026 and ends on June 30, 2026 must file by September 15, 2026.

Extensions: Time to File, Not Time to Pay

Form 7004 requests an automatic extension of time to file. Publication 509 says it gives six months for Form 1120. The IRS Form 1120 instructions say you generally file it by the regular due date.

The critical point: an extension to file does not extend the time to pay. Interest and penalties on unpaid tax still run from the original due date. A corporation that expects to owe should pay an estimate with the extension.

Estimated Tax Payments

Who must pay

The Form 1120 instructions say installments are required if the corporation expects total tax of $500 or more for the year, after applicable credits.

When

Installments are due on the 15th day of the 4th, 6th, 9th and 12th months of the tax year. For a calendar-year corporation, that is April 15, June 15, September 15 and December 15.

How to pay

Estimated payments must be made by electronic funds transfer. The IRS lists these options:

• EFTPS: free. Same-day payments of $1 million or less are accepted before 3:00 p.m. Eastern on a business day.
• IRS business tax account: free electronic payments.
• Same-day wire: available through the Federal Tax Collection Service if an EFTPS deposit was not submitted on time. Your bank may charge a fee.

Worked example

A corporation expects $120,000 of tax for 2026. A simple even split would be four installments of $30,000. Real calculations can differ, because the rules allow other methods and exceptions. Use Form 2220 and the instructions to check.

For deeper help planning payments, read our guide to calculating your tax before meeting an accountant.

Penalties for Late Filing and Late Payment

Per the Form 1120 instructions:

Interest also applies to unpaid tax.

Worked example

A corporation owes $50,000 and files two months late.

• Late-filing penalty: 5% × 2 months = 10%, or $5,000
• Late-payment penalty: 0.5% × 2 months = 1%, or $500

The instructions explain how the two penalties interact when both apply, so the actual total may be lower. Either way, filing on time, even without full payment, usually costs far less than filing late.

Underpayment penalty

If installments are too small or late, the corporation may owe a penalty under IRC §6655. Form 2220 calculates it.

Corporate Alternative Minimum Tax (CAMT)

The IRS describes the CAMT as a 15% minimum tax on adjusted financial statement income (AFSI), created by the Inflation Reduction Act of 2022 for taxable years beginning after December 31, 2022.

• Who: generally large corporations with average annual financial statement income above $1 billion. Lower thresholds can apply to certain foreign-parented groups, so check the Form 4626 instructions.
• Form: Form 4626.
• Relief: the IRS has issued several relief measures for underpayment of estimated tax tied to CAMT. For tax year 2025, the Form 1120 instructions say the IRS will continue waiving the §6655 penalty for estimated payments attributable to CAMT liability.

Most small and mid-sized companies are not subject to the CAMT.

C Corporation vs S Corporation Taxes

An S corporation generally passes income to shareholders, who report it on their own returns. Eligibility rules apply, so see the Form 2553 instructions.

Double taxation example

A C corporation earns $100,000 of pre-tax profit.

1. Corporate tax at 21%: $21,000
2. Left to distribute: $79,000
3. Shareholder pays 15% on a qualified dividend: $11,850
4. Total federal tax: $32,850 (32.85%)

This ignores state taxes and the 3.8% Net Investment Income Tax. It shows why many small businesses choose pass-through structures, and why many larger businesses accept C corporation status anyway.

Federal vs State Corporate Taxes

The federal 21% is only one layer. States set their own rules, and the taxes differ in kind, not just in rate:

• Some states have a corporate income tax.
• Some use a franchise tax, for example Texas's franchise tax.
• Some use gross receipts taxes, such as Ohio's commercial activity tax, Washington's business and occupation tax, Nevada's commerce tax and Oregon's corporate activity tax.

Do not call every state business tax an "income tax." A gross receipts tax applies to revenue, not profit. Also, a company with operations in several states may need to apportion its income and register where it has nexus.

For individual-level comparisons, read our federal vs state income tax in the USA, state income tax 2026 and the US state income tax calculator. For the broader concept, see direct vs indirect tax.

Always check each state's revenue department for rates, bases and due dates.

Foreign-Owned US Corporations

A corporation organized in the United States is a domestic corporation, even if foreign investors own it. It generally files Form 1120 and pays the same 21% rate. A foreign corporation with US activity may file Form 1120-F, which has its own rules. If your structure crosses borders, speak with a tax adviser.

Recordkeeping and Audit Readiness

Good records make filing faster and reduce audit risk.

• Keep financial statements, general ledgers, bank statements and invoices.
• Keep depreciation schedules and asset purchase documents.
• Keep board minutes and loan agreements.
• Keep support for credits, charitable gifts and NOL carryforwards.

See our guide on IRS audit triggers and common income tax calculator mistakes for examples of what attracts attention.

A Practical Compliance Checklist

1. Confirm your entity type. C corporation, S corporation or something else.
2. Confirm your tax year. Calendar or fiscal.
3. Mark your calendar. Filing date, extended date, and four installment dates.
4. Estimate tax early. If you expect $500 or more, plan installments.
5. Pay electronically. Set up EFTPS or an IRS business tax account.
6. File Form 7004 on time if you need more time, and pay an estimate with it.
7. Review new deductions. Check bonus depreciation, research expensing and the interest limit.
8. Check state obligations. Franchise, gross receipts or income tax.
9. Keep records. Organize support for every deduction and credit.
10. Review with a CPA. Especially for large transactions or multistate activity.

If you also sell goods online, our guide on sales tax on online purchases in the USA covers a separate obligation.

Common Mistakes

• Confusing extension to file with extension to pay
• Ignoring estimated tax until the year-end return
• Treating a state gross receipts tax as an income tax
• Assuming book profit equals taxable income
• Missing the S corporation date. It is March 15, not April 15.
• Filing without e-file when required
• Forgetting to confirm 2025 law changes before claiming deductions

Frequently Asked Questions

What is the US corporate income tax rate in 2026?

The federal rate is a flat 21% of taxable income under IRC §11(b).

Is the federal corporate tax rate still 21% in 2026?

Yes. The statute I checked says 21 percent. Always confirm against any new legislation.

When are corporate income taxes due in 2026?

A calendar-year corporation's Form 1120 for tax year 2025 was due April 15, 2026, or October 15, 2026 if extended. For tax year 2026, it is generally due April 15, 2027.

What is the deadline for filing Form 1120?

The 15th day of the 4th month after the tax year ends. For June 30 fiscal-year corporations, the IRS rule is the 15th day of the 3rd month.

Do all US corporations have to file an income tax return?

Domestic corporations generally must file Form 1120 even with no taxable income, unless exempt under section 501. S corporations file Form 1120-S.

How do corporations pay estimated federal income taxes?

By electronic funds transfer, for example through EFTPS or an IRS business tax account, in installments due in the 4th, 6th, 9th and 12th months of the tax year.

What happens if a corporation misses its tax filing deadline?

Penalties apply: 5% of unpaid tax per month (up to 25%) for late filing, and ½ of 1% per month (up to 25%) for late payment, plus interest.

Can a corporation get an extension to file?

Yes, with Form 7004. It gives six months for Form 1120, but it does not extend the time to pay.

Does a tax extension also extend the payment deadline?

No. Pay your estimated balance by the original due date to limit penalties and interest.

What is the corporate alternative minimum tax?

A 15% minimum tax on adjusted financial statement income, generally for corporations averaging above $1 billion of income, reported on Form 4626.

Are state corporate taxes separate from federal taxes?

Yes. States may impose income, franchise or gross receipts taxes, and each has its own rules.

What is the difference between C and S corporation taxation?

A C corporation pays 21% at the entity level, and shareholders pay tax on dividends. An S corporation generally passes income through to shareholders.

Where can I find official IRS corporate tax instructions?

Start with the Instructions for Form 1120, Publication 509 and Publication 542. Cross-country filing dates are also summarized in our tax filing deadlines by country guide.

Your Next Steps

1. If you extended your 2025 return, file by October 15, 2026.
2. Check whether your December 15 estimated installment is due.
3. Review your 2026 deductions, especially equipment purchases and research costs.
4. Confirm your state filing requirements.
5. Book a review with a CPA before year-end.

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