What is corporation tax? Rates, rules, and deductions

Corporation tax is a federal tax on the profits your C corporation earns each year. Unlike sales tax or payroll tax, it applies to what your company keeps after subtracting allowable business expenses from total revenue.

The federal rate sits at a flat 21%, set by the Tax Cuts and Jobs Act of 2017. How much you owe depends on your business structure, eligible deductions, and where you operate.

What is corporation tax?

Corporation tax is a tax on the net income of incorporated businesses. If your company is a C corporation, the IRS treats it as a separate taxpaying entity. That means the business itself owes federal income tax on its profits, independent of what you pay on your personal return.

Most small businesses are taxed differently. Sole proprietorships, partnerships, and S corporations pass income through to the owners' personal tax returns. C corporations don't get that treatment. The company files its own return, pays its own tax, and distributes what's left to shareholders afterward.

How is corporation tax calculated?

Taxable income vs. gross revenue

Your corporation tax bill starts with gross revenue, but you don't pay taxes on all of it. The IRS taxes your net income, which is what remains after you subtract all allowable business expenses.

Expenses like rent, employee wages, and advertising all reduce the amount of income subject to tax. The gap between gross revenue and taxable income can be substantial, so accurate expense tracking matters when you file.

Deductions that lower your tax bill

Beyond day-to-day operating costs, you can deduct several categories of expenses that lower your tax bill.

• Depreciation: Lets you spread the cost of large asset purchases like equipment, vehicles, or technology over their useful life rather than expensing them all at once
• Research and development: Qualifies for its own deduction, and in some cases an additional R&D tax credit
• Employee healthcare contributions: Deductible as a business expense, giving you a financial incentive to offer benefits beyond attracting talent

Clean, categorized records of deductible expenses throughout the year make filing more accurate and reduce the chance of missing eligible deductions.

Which businesses pay corporation tax?

C corporations

C corporations are the only business structure that pays federal corporation tax directly. The IRS recognizes a C corp as a legal entity separate from its owners, so the business files its own tax return (Form 1120) and pays tax on its profits at the federal rate.

Most publicly traded companies are C corporations. Many private companies also choose this structure to raise outside capital, offer stock options, or retain earnings at a potentially lower rate than the owners' personal income tax brackets.

Pass-through entities

S corporations, partnerships, limited liability companies (LLCs), and sole proprietorships are all considered pass-through entities for federal tax purposes. Their profits flow directly to the owners' personal tax returns.

The business itself doesn't file a separate corporate tax return or owe corporation tax. Instead, each owner reports their share of the business income on their personal return and pays at their individual rate. This avoids the double taxation problem that C corporations face, which is a major reason many smaller businesses choose pass-through structures.

Corporation tax rates in the US

The federal rate

The federal corporation tax rate is a flat 21%. The Tax Cuts and Jobs Act of 2017 set this rate, replacing the previous graduated system that topped out at 35%. Every C corporation pays the same percentage regardless of how much income it earns.

Before 2018, smaller corporations paid lower rates on their first $75,000 of income. That tiered structure no longer exists. Whether your company earns $100,000 or $100 million in taxable income, the federal rate is 21%.

State and local corporate taxes

On top of the federal rate, most states impose their own corporate income tax. State rates range from about 2% to 11.5%, which means your combined federal-and-state rate could be well above 21%.

The average combined rate across all states is about 25.5%. However, six states don't impose a state corporate income tax, including Texas, Nevada, Wyoming, Washington, South Dakota, and Ohio. Some of these states use alternative business taxes like gross receipts taxes, but they don't impose a traditional income-based corporate tax.

Where you incorporate and where you operate both affect your state tax obligations. If you do business in multiple states, you may owe taxes in each one based on how much revenue, payroll, or property you have in each state.

What does double taxation mean for shareholders?

Double taxation means corporate profits get taxed twice: once when the corporation earns them, and again when shareholders receive dividends from those after-tax profits.

Say your company earns $1 million in net income and pays 21% in federal corporation tax, leaving $790,000. If the company distributes that $790,000 as dividends, each shareholder then pays personal income tax on the dividend income they receive. Depending on whether those dividends are qualified, the shareholder's rate could be 0%–20% at the federal level.

The combined effect is that a dollar of corporate profit can lose 30%–40% of its value by the time it reaches a shareholder's bank account. That's why many private companies choose pass-through structures, and why C corporations often retain earnings rather than distributing them.

What is the global minimum corporate tax?

A global agreement reached in 2021 set a floor of 15% on corporate tax rates worldwide, with over 130 countries signing on. The goal is to curb profit-shifting, where multinational corporations route taxable income through low-tax jurisdictions to avoid paying higher rates in the countries where they do business.

Under this framework, if a multinational's effective tax rate in a given country falls below 15%, the company's home country can impose a top-up tax to bring the rate to the minimum. This reduces the incentive for companies to set up shell entities in tax havens purely for tax purposes.

For US-based C corporations, the 21% federal rate already exceeds the global minimum. The agreement also changes how foreign subsidiaries and international revenue get treated. If your company operates across borders, the global minimum affects how you structure your international entities and where you book income.

Who bears the cost of corporation tax?

The corporation pays the tax, but economists have long debated who actually bears the cost. Shareholders feel it most directly through lower after-tax returns. Companies facing higher tax costs sometimes reduce what they pay employees, particularly in thin-margin industries, and consumers can end up paying more if companies raise prices to protect margins.

How much falls on each group depends on factors like industry competition, labor market conditions, and how sensitive demand is to price changes. In highly competitive industries, companies have less room to pass costs to customers, and more pressure lands on shareholders and workers.

How to stay on top of your corporate tax obligations

Keep clean financial records year-round

Reconciling accounts and categorizing expenses as they occur reduces the risk of missed deductions, errors, and penalties at filing time.

Accounting software that tracks expenses in real time and categorizes transactions automatically reduces the chance of errors in tax preparation.

Maximize your eligible deductions

Regular review of deductible expenses, rather than only at year-end, helps surface all eligible reductions. Depreciation schedules, R&D credits, employee benefit contributions, and business travel costs all reduce taxable income when tracked and claimed correctly.

Plan for estimated tax payments

C corporations must make estimated tax payments quarterly. If you underpay, the IRS charges interest and penalties. Including estimated payments in cash flow planning helps avoid shortfalls.

Work with a qualified tax professional

Tax law changes regularly, and the interaction between federal, state, and international tax obligations is complex. A CPA or tax advisor who specializes in corporate tax can identify eligible deductions and keep filings compliant.

Use financial operations software

Incomplete expense reports, disorganized receipts, or a slow month-end close reduce the accuracy of your tax return.

Financial operations platforms that automate expense categorization, enforce spending policies, and maintain audit-ready records throughout the year reduce the manual work required at tax time.

Keep your expense records tax-ready with Ramp

Ramp is a spend management platform that automates expense tracking and accounting for finance teams.

From employee expenses, vendor payments, software subscriptions, and travel, Ramp automatically categorizes each transaction as it happens, applying your chart of accounts and custom coding rules so nothing sits uncoded at quarter-end.

Receipts are captured at the point of purchase and matched to the corresponding card transaction without manual data entry. Ramp syncs coded transactions directly to QuickBooks, Xero, NetSuite, Sage Intacct, and more, so when your CPA pulls the books, your deductible expenses are already organized by GL account.

Get started with Ramp.