Tax forms
Form 1120: who files the C corp tax return, when it's due and how it's laid out
IRS Form 1120 is the U.S. corporation income tax return. See who must file it, the April 15 due date and the June 30 fiscal-year exception, every schedule on the six-page form, the $250,000 and $500,000 thresholds, penalties and record rules.
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The quick answer
Form 1120, U.S. Corporation Income Tax Return, is the IRS form a domestic corporation uses to report its income, gains, losses, deductions and credits and to figure its income tax. Every domestic corporation not exempt under section 501 must file it, even with no taxable income, by the 15th day of the 4th month after its tax year ends (April 15 for a calendar-year corporation). Form 7004 gives an automatic 6-month extension to file, not to pay.
Who must file Form 1120
The IRS instructions say that, unless exempt under section 501, all domestic corporations must file an income tax return whether or not they have taxable income. That includes corporations in bankruptcy. Domestic corporations file Form 1120 unless they are required, or elect, to file a special return.
An LLC files Form 1120 only if it has filed Form 8832 to elect to be treated as an association taxable as a corporation. By default, an LLC with more than one owner is treated as a partnership and files Form 1065, and a single-member LLC is disregarded and reports on its owner's return. A domestic entity that elects corporate treatment also attaches a copy of Form 8832 to Form 1120 for the year of the election.
A few other cases also use Form 1120. A corporation that farms (other than a subchapter T cooperative) reports that income on it. A domestic disregarded entity wholly owned by a foreign person must file a pro forma Form 1120 with Form 5472 attached by the due date, including extensions. A corporation that self-certifies as a qualified opportunity fund files Form 1120 with Form 8996 attached, even with no income or expenses.
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| If the organization is | It files |
|---|---|
| S corporation (section 1361) | Form 1120-S |
| LLC treated as a partnership | Form 1065 |
| Foreign corporation (other than certain insurance companies) | Form 1120-F |
| Homeowners association that elects under section 528 | Form 1120-H |
| Life insurance company (section 801) | Form 1120-L |
| Subchapter T cooperative, including a farmers' cooperative | Form 1120-C |
| Political organization (section 527) | Form 1120-POL |
| Exempt organization with unrelated business income | Form 990-T |
Form 1120 due date, extension and payment
A corporation generally files Form 1120 by the 15th day of the 4th month after its tax year ends. For a calendar-year corporation that is April 15. A corporation with a fiscal year ending June 30 files by the 15th day of the 3rd month after its year ends instead. If the due date falls on a Saturday, Sunday or legal holiday, the corporation can file on the next business day.
Form 7004 requests an automatic 6-month extension of time to file Form 1120. It generally must be filed by the return's regular due date. The extension covers filing only. Any tax due must be paid in full by the original due date, not including extensions.
Corporations must use electronic funds transfer for all federal tax deposits, including corporate income tax. That can be done through the Electronic Federal Tax Payment System (EFTPS) or the corporation's IRS business tax account. The IRS says both are free.
A corporation that expects its total tax for the year (less applicable credits) to be $500 or more must pay estimated tax in installments. They are due by the 15th day of the 4th, 6th, 9th and 12th months of the tax year, moving to the next business day when a date falls on a weekend or legal holiday. For a calendar-year corporation those months are April, June, September and December.
When a corporation must e-file
For returns filed on or after January 1, 2024, a corporation must e-file Form 1120 if it files 10 or more returns of any type during the calendar year. The count includes income tax, employment tax, excise tax and information returns, so a small corporation with a handful of employees and contractors can reach it quickly.
The return must be signed and dated by the president, vice president, treasurer, assistant treasurer, chief accounting officer or another corporate officer authorized to sign, such as a tax officer.
Page 1, line by line
Page 1 runs from income down to the amount owed or overpaid. The lines below are from the 2025 Form 1120.
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| Lines | What goes there |
|---|---|
| 1a to 1c | Gross receipts or sales, less returns and allowances |
| 2 and 3 | Cost of goods sold (attach Form 1125-A), then gross profit |
| 4 to 10 | Dividends and inclusions from Schedule C, interest, gross rents, gross royalties, capital gains, Form 4797 gains and other income |
| 11 | Total income: lines 3 through 10 |
| 12 to 27 | Deductions, starting with compensation of officers on line 12. Line 27 is total deductions |
| 28 | Taxable income before the net operating loss deduction and special deductions: line 11 minus line 27 |
| 29a to 29c | Net operating loss deduction and special deductions from Schedule C |
| 30 | Taxable income: line 28 minus line 29c |
| 31 | Total tax, carried from Schedule J |
| 33 | Total payments and credits, from Schedule J |
| 34 | Estimated tax penalty (check the box if Form 2220 is attached) |
| 35 and 36 | Amount owed, or overpayment |
| 37 | Overpayment credited to next year's estimated tax or refunded, with new direct deposit lines 37c to 37e |
- Line 12: if total receipts (line 1a plus lines 4 through 10) are $500,000 or more, the corporation completes Form 1125-E, Compensation of Officers, and enters its line 4 total here.
- Line 18: business interest expense is generally limited under section 163(j) to business interest income, plus 30% of adjusted taxable income, plus floor plan financing interest. The limit is figured on Form 8990.
- Line 19: charitable contributions are generally limited to 10% of taxable income, figured with certain changes. The excess can be carried over to the next 5 tax years.
The schedules on pages 2 to 6
Form 1120 is six pages. Page 1 is the summary above. The rest are schedules that feed it.
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| Test | Result |
|---|---|
| Total receipts for the year and total assets at year end both less than $250,000 (Schedule K, question 13) | Schedules L, M-1 and M-2 are not required |
| Total receipts of $500,000 or more | Attach Form 1125-E for officer compensation |
| Total assets of $10 million or more at year end | File Schedule M-3 instead of Schedule M-1 |
| 10 or more returns of any type filed in the calendar year | E-file Form 1120 |
- Schedule C (page 2): dividends, inclusions and special deductions. Its totals go to lines 4 and 29b.
- Schedule J (page 3): tax computation and payments. Its totals go to lines 31 and 33.
- Schedule K (pages 4 and 5): other information, answered mostly yes or no. If any individual or estate owns directly 20% or more, or directly or indirectly 50% or more, of the voting stock, the corporation completes Part II of Schedule G. If one foreign person owns at least 25% of the voting power or value, Form 5472 may be needed.
- Schedule L (page 6): balance sheets per books at the start and end of the year.
- Schedule M-1 (page 6): reconciles income per books with income per return. A corporation with total assets of $10 million or more on the last day of the year files Schedule M-3 instead.
- Schedule M-2 (page 6): analysis of unappropriated retained earnings per books.
Penalties and interest
A corporation that doesn't file by the due date, including extensions, may be charged 5% of the unpaid tax for each month or part of a month the return is late, up to 25%. For a return required to be filed in 2026 that is more than 60 days late, the minimum penalty is the smaller of the tax due or $525. The penalty isn't charged if the corporation shows reasonable cause.
A corporation that doesn't pay on time may generally be charged 1/2 of 1% of the unpaid tax for each month or part of a month it stays unpaid, up to 25%. Interest is charged on tax paid late even when an extension to file was granted, at a rate set under section 6621.
Underpaid estimated tax is a separate penalty, figured on Form 2220 and entered on line 34. It generally applies when the tax is $500 or more and the corporation didn't pay at least the smaller of its current year tax or its prior year's tax on time. A corporation that overpaid estimated tax may be able to get a quick refund with Form 4466.
Accounting method, records and amended returns
A corporation can't use the cash method unless it is a small business taxpayer. For tax years beginning in 2025, that means average annual gross receipts of $31 million or less for the 3 prior tax years, and not being a tax shelter. Changing an accounting method generally needs IRS consent on Form 3115, and changing a tax year generally needs Form 1128.
Records that support income, deductions or credits on the return usually must be kept for 3 years from the date the return is due or filed, whichever is later. Records that show basis in property are kept as long as they are needed to figure the basis of the original or replacement property. The IRS also says to keep copies of all filed returns.
To correct a Form 1120 that was already filed, a corporation uses Form 1120-X.
Aldro prepares and files Form 1120 and its state returns. Our team handles the whole return, schedules included, for one flat yearly price that covers everything tax.
Worked example
Say a calendar-year corporation has $400,000 of gross receipts, $5,000 of returns and allowances and $150,000 of cost of goods sold, with no dividends, interest, rents or other income. Line 1c is $395,000 and gross profit on line 3 is $245,000, which is also total income on line 11. Its deductions are $90,000 of officer compensation, $50,000 of salaries and wages, $24,000 of rent and $16,000 of other deductions, so line 27 is $180,000. Line 28 is $245,000 minus $180,000 = $65,000. With no net operating loss or special deductions, taxable income on line 30 is $65,000, and the tax is then figured on Schedule J. Total receipts are $400,000 (line 1a plus lines 4 through 10), so Form 1125-E isn't required, because that starts at $500,000. Schedules L, M-1 and M-2 are required, because receipts are over $250,000. If the return showed $10,000 of unpaid tax and was filed 3 months late with no extension, the late filing penalty would be 5% x 3 = 15% of $10,000 = $1,500. Interest and the late payment penalty are figured separately.
Common questions
Who has to file Form 1120?
Every domestic corporation not exempt under section 501, including one in bankruptcy, whether or not it has taxable income, unless it files a special return such as Form 1120-S. An LLC files Form 1120 only if it filed Form 8832 to be taxed as a corporation.
When is Form 1120 due?
By the 15th day of the 4th month after the tax year ends, which is April 15 for a calendar-year corporation. A corporation with a June 30 year end files by the 15th day of the 3rd month. A weekend or legal holiday moves the date to the next business day.
How do I get an extension for Form 1120?
File Form 7004 by the regular due date. It gives an automatic 6-month extension of time to file. It doesn't extend the time to pay, so tax is still due by the original date.
Does every corporation fill out Schedule L and Schedule M-1?
No. If total receipts for the year and total assets at year end are both under $250,000, Schedule K question 13 says Schedules L, M-1 and M-2 aren't required.
What is the penalty for filing Form 1120 late?
5% of the unpaid tax for each month or part of a month late, up to 25%. For a return due in 2026 that is more than 60 days late, the minimum is the smaller of the tax due or $525.
How long should a corporation keep records for Form 1120?
Usually 3 years from the date the return is due or filed, whichever is later. Records that show basis in property are kept as long as they are needed to figure basis.
Aldro
The cheapest way to get your business taxes done: $399 flat.
Business tax filing is $399 USD a year, and it covers everything tax for that year.
How it works
- Tell us about your business. A two-minute form. No payment is collected through it.
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What's included
$399 a year covers everything tax for that tax year.
- Every business return for the year. All the federal and state or provincial business returns you need for the tax year: Schedule C, 1065, 1120-S, 1120 and their state returns in the US; T2, or T1 with T2125, in Canada.
- More than one state. Multi-state returns are included at the same price.
- Your personal return. The owner’s personal return (1040 or T1) is included when it’s needed for the business income.
- Quebec. Quebec returns (CO-17, TP-1 and TP-80) are included, and our Quebec pages are in French.
- Extensions and reminders. Extensions (Form 7004 or 4868) and quarterly estimate reminders are included.
- Information returns. 1099-NEC, T4/T4A and T5018 slips are included in the tax price.
- Unfiled past years. Each unfiled prior-year return is $399 per tax year, the same flat price.
- Bookkeeping at $20 a month. Unlimited bank and card accounts, monthly reconciliation and monthly statements.
Payroll processing and sales-tax filing aren’t included in bookkeeping. Prices are in USD. Our team prepares and files your return.
Sources
- IRS: Instructions for Form 1120 · checked October 31, 2026
- IRS: Form 1120 (2025) · checked October 31, 2026
- IRS: Publication 509, Tax Calendars (draft) · checked October 31, 2026
This guide explains general rules from the sources listed. It isn’t tax advice for your situation.