Fill out 1120 (U.S. Corporation Income Tax Return) online
Form 1120 is the annual income tax return filed by C corporations in the United States. It reports the corporation's income, gains, losses, deductions, and credits, and calculates the corporate income tax owed.
How to fill out 1120 (U.S. Corporation Income Tax Return)
Enter corporation details
Fill in the corporation name, address, EIN, date of incorporation, total assets, and business activity code at the top of the form. Select the applicable accounting method.
Report gross income
Enter gross receipts or sales on line 1a, subtract returns and allowances, then report cost of goods sold (Schedule A) on line 2. Include dividends (Schedule C), interest, rents, royalties, and capital gains in lines 4-10.
Claim deductions
Report deductions for officer compensation, salaries and wages, repairs, bad debts, rents, taxes, interest, depreciation (Form 4562), advertising, and other deductions in lines 12-26. Calculate taxable income before special deductions on line 28.
Compute tax and credits
Calculate total tax on line 31 using the applicable corporate tax rate. Apply any credits (general business credit, prior year minimum tax credit) on Schedule J to reduce the amount owed.
Report payments and balance due
Enter estimated tax payments, tax deposits, and credits on Schedule J. Determine whether the corporation has an overpayment (refund or applied to next year) or a balance due.
Complete required schedules
Attach Schedule K (Other Information), Schedule L (Balance Sheets), Schedule M-1 (Income Reconciliation), and Schedule M-2 (Retained Earnings Analysis). Corporations with total assets of $10 million or more must file Schedule M-3 instead of M-1.
About 1120 (U.S. Corporation Income Tax Return)
Who needs this form
All domestic C corporations must file Form 1120 each year, regardless of whether they had taxable income. This includes corporations that were inactive during the year. S corporations file Form 1120-S instead.
Where to submit
File with the IRS by the deadline in the latest Form 1120 instructions (calendar-year corporations are typically due on April 15). An automatic 6-month extension is available by filing Form 7004 before the original deadline.
Source and content freshness
- Reviewed: 2026-02-24
- Check the latest official form instructions for the filing year that applies to you.
- Filing deadlines may shift for weekends and holidays. Verify due dates with official instructions.
Common mistakes to avoid
- Forgetting to reconcile book income to taxable income on Schedule M-1 or M-3
- Missing the estimated tax payment deadlines, resulting in underpayment penalties
- Not properly separating shareholder-employee compensation from dividends
- Failing to attach required schedules (Schedule D, Form 4562) when applicable
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What is the difference between Form 1120 and Form 1120-S?
Form 1120 is for C corporations that pay corporate income tax directly. Form 1120-S is for S corporations, which are pass-through entities where income flows to shareholders' individual returns. C corporations face double taxation (corporate tax plus shareholder tax on dividends), while S corporations are taxed only at the shareholder level.
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