C Corporation
Taxable Income

Master how to calculate taxable income for C corporations: from gross income through deductions to the final tax liability.

CPA Regulation (REG)

What Is a C Corporation?

A C corporation is a legal entity that is separate from its owners for tax purposes. It files its own tax return (Form 1120) and pays tax at the corporate level. When profits are distributed as dividends, shareholders pay tax again: this is called double taxation.

Separate Entity

The corporation is taxed independently from its shareholders.

Double Taxation

Income is taxed at corporate level, then dividends are taxed to shareholders.

Form 1120

The annual U.S. corporate income tax return filed with the IRS.

Why Taxable Income Matters

Taxable income is the foundation for computing a C corporation's tax liability. Getting it right means understanding which items are included, which are excluded, and which deductions have special limitations.

The Income Flow Overview

Components of Gross Income

Corporate gross income includes all income from whatever source derived, unless specifically excluded by the IRC. Key components include:

1

Gross profit on sales: Sales revenue minus cost of goods sold (COGS)

2

Dividends received from investments in other corporations

3

Interest income, rents, royalties, and capital gains

4

Other income: discharge of indebtedness, recovery of bad debts, etc.

The Core Formula

Key Corporate Deductions

Compensation

Salaries, wages, and bonuses: must be reasonable for services performed.

Depreciation

MACRS depreciation on business property, including Section 179 expensing.

Charitable Contributions

Limited to 10% of taxable income (before the charitable deduction and DRD).

Net Capital Loss

Cannot deduct against ordinary income. Carry back 3 years, forward 5 years.

Organizational Costs

Deduct up to $ \$5{,}000 $ in first year (reduced if costs exceed $ \$50{,}000 $).

The Dividends Received Deduction

The DRD reduces the effect of triple taxation when one corporation receives dividends from another. The deduction percentage depends on the ownership percentage:

Ownership %	DRD %	Taxable Income Limit?
< 20%	50%	Yes: 50% of TI
20% to < 80%	65%	Yes: 65% of TI
80% or more	100%	No limit

C Corp vs. S Corp

Feature	C Corporation	S Corporation
Tax Level	Corporate level	Shareholder level (pass-through)
Tax Rate	Flat 21%	Individual rates
Double Taxation	Yes	No
DRD Available	Yes	No
Charitable Limit	10% of TI	Flows to shareholders
Tax Return	Form 1120	Form 1120-S

Charitable Contribution Limitation

A C corporation's charitable contribution deduction is limited to 10% of taxable income, computed before the charitable deduction, the DRD, any NOL carryback, and any capital loss carryback.

How to Calculate C Corp Taxable Income

1

Start with gross receipts. Include all sales revenue and other income sources.

2

Subtract COGS to arrive at gross profit.

3

Add other income: dividends, interest, rents, royalties, capital gains.

4

Subtract ordinary deductions (compensation, rent, depreciation, etc.).

5

Apply the charitable limitation (10% of modified TI). Carry forward excess.

6

Subtract the DRD (apply TI limitation unless it creates an NOL).

7

Result: Taxable Income. Multiply by 21% for the tax liability.

Example 1: Basic Calculation

Example 2: Charitable Limitation

A C corporation has total income of $ \$500{,}000 $, ordinary deductions of $ \$300{,}000 $ (excluding charitable), and made $ \$30{,}000 $ in charitable contributions. Dividend income is $ \$0 $.

1

Modified TI: $ \$500{,}000 - \$300{,}000 = \$200{,}000 $

2

10% limit: $ \$200{,}000 \times 10\% = \$20{,}000 $

3

Allowed deduction: $ \$20{,}000 $ (not the full $ \$30{,}000 $)

4

Carryforward: $ \$10{,}000 $ excess carried forward up to 5 years

Example 3: DRD Limitation

Corp X owns 25% of Corp Y and receives $ \$100{,}000 $ in dividends. Corp X's taxable income before the DRD is $ \$120{,}000 $.

1

Ownership is 25% (20%–80%): DRD rate = 65%

2

DRD on dividends: $ \$100{,}000 \times 65\% = \$65{,}000 $

3

TI limitation: $ \$120{,}000 \times 65\% = \$78{,}000 $

4

DRD allowed: Lesser of $ \$65{,}000 $ or $ \$78{,}000 $ = $ \$65{,}000 $

Common Mistakes

✕ Using Net Capital Losses

C corps cannot deduct net capital losses against ordinary income. They carry back 3 / forward 5 years only.

✕ Wrong Charitable Base

The 10% limit uses modified TI (add back charitable deduction and DRD). Don't use regular TI.

✕ Ignoring the DRD TI Limit

The DRD is limited by taxable income unless taking the full DRD creates or increases an NOL.

✕ Deducting Federal Income Tax

Federal income tax paid is never deductible by a C corporation. State taxes are deductible.

✕ Unreasonable Compensation

Salaries to shareholder-employees must be reasonable. Excess is reclassified as a nondeductible dividend.

Key Deduction Limits Summary

Deduction	Limitation	Carryover
Charitable Contributions	10% of modified TI	Forward 5 years
DRD (< 20%)	50% of TI (unless NOL)	N/A
DRD (20% to < 80%)	65% of TI (unless NOL)	N/A
DRD (80%+)	100%, no TI limit	N/A
Net Capital Losses	Cannot offset ordinary income	Back 3, Forward 5
Net Operating Loss	80% of TI (post-2017)	Forward indefinitely
Organizational Costs	Up to $ \$5{,}000 $ in Year 1	Amortize 180 months

Question 1 of 5

A C corporation has gross income of $ \$600{,}000 $ and total deductions (before DRD) of $ \$400{,}000 $. It received $ \$50{,}000 $ in dividends from a corporation in which it owns 10%. What is the DRD?

With less than 20% ownership, the DRD is 50%. $ \$50{,}000 \times 50\% = \$25{,}000 $. The TI before DRD is $ \$200{,}000 $, and 50% of that is $ \$100{,}000 $, so the TI limitation does not further reduce the DRD.

Question 2 of 5

A C corporation has taxable income of $ \$300{,}000 $ before charitable contributions. It donated $ \$50{,}000 $ to qualified charities. What is the maximum charitable contribution deduction this year?

The charitable contribution deduction is limited to 10% of modified taxable income. $ \$300{,}000 \times 10\% = \$30{,}000 $. The remaining $ \$20{,}000 $ is carried forward up to 5 years.

Question 3 of 5

Which of the following is NOT deductible by a C corporation?

Federal income taxes are never deductible by a corporation. State and local income taxes, reasonable compensation, and depreciation are all allowable deductions.

Question 4 of 5

A C corporation has a net capital loss of $ \$40{,}000 $ for the current year. How should this loss be treated?

C corporations cannot deduct net capital losses against ordinary income (the $ \$3{,}000 $ rule applies only to individuals). Corporate net capital losses are carried back 3 years and forward 5 years as short-term capital losses.

Question 5 of 5

Corp A owns 85% of Corp B and receives $ \$200{,}000 $ in dividends. Corp A's taxable income before the DRD is $ \$150{,}000 $. What is the DRD?

With 80% or more ownership, the DRD is 100% and there is no taxable income limitation. The full $ \$200{,}000 $ is deductible, even though TI before DRD is only $ \$150{,}000 $.

C CorporationTaxable Income

What Is a C Corporation?

Why Taxable Income Matters

The Income Flow Overview

Components of Gross Income

The Core Formula

Key Corporate Deductions

The Dividends Received Deduction

C Corp vs. S Corp

Charitable Contribution Limitation

How to Calculate C Corp Taxable Income

Example 1: Basic Calculation

Example 2: Charitable Limitation

Example 3: DRD Limitation

Common Mistakes

Key Deduction Limits Summary

Question 1 of 5

Question 2 of 5

Question 3 of 5

Question 4 of 5

Question 5 of 5

C Corporation
Taxable Income