Fill out 1120-S (U.S. Income Tax Return for an S Corporation) online
Form 1120-S is the annual tax return filed by S corporations. Like partnerships, S corporations are pass-through entities: the corporation reports its income, deductions, and credits, but the tax liability passes through to individual shareholders.
How to fill out 1120-S (U.S. Income Tax Return for an S Corporation)
Enter corporation information
Fill in the corporation name, address, EIN, date of S election, business activity code, and accounting method at the top of the form.
Report income and deductions
Enter gross receipts on line 1a, cost of goods sold on line 2, and compute gross profit. Report deductions for officer compensation, salaries, rent, taxes, interest, and depreciation in lines 7-19. Calculate ordinary business income on line 21.
Complete Schedule K
Report the S corporation totals: ordinary income, rental activity income, interest, dividends, royalties, capital gains/losses, Section 179 deduction, and charitable contributions.
Prepare Schedule K-1 for each shareholder
Issue a Schedule K-1 to each shareholder showing their pro-rata share of income, deductions, and credits based on their ownership percentage and the days they held shares during the year.
Complete balance sheets and reconciliation
File Schedule L (Balance Sheets), Schedule M-1 (Reconciliation of Income), and Schedule M-2 (Accumulated Adjustments Account) if total assets are $250,000 or more.
About 1120-S (U.S. Income Tax Return for an S Corporation)
Who needs this form
Any domestic corporation that has elected S corporation status by filing Form 2553. The S corporation must file Form 1120-S even if it had no income or deductions for the year.
Where to submit
File with the IRS by the deadline listed in the latest Form 1120-S instructions (calendar-year S corporations are typically due in mid-March). Extensions are available using Form 7004; verify the current extended due date in the official instructions.
Source and content freshness
- Reviewed: 2026-02-16
- 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
- Filing late (penalty is per shareholder per month)
- Not issuing Schedule K-1 to each shareholder by the filing deadline
- Paying shareholder-employees unreasonably low salaries to reduce payroll taxes
- Not tracking shareholder basis, leading to incorrect loss deductions
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What is the difference between an S corporation and a C corporation?
An S corporation is a pass-through entity: profits and losses flow through to shareholders and are taxed on their individual returns. A C corporation pays corporate income tax, and shareholders pay tax again on dividends (double taxation). S corporations avoid double taxation but have restrictions on the number and type of shareholders. To elect S corporation status, file Form 2553.
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