Form 1120: the C corporation return

A C corporation is a taxpayer in its own right, and Form 1120 is where it works out and pays its tax. This guide covers who files it, how the return is structured, the schedules small corporations can skip, and the extra reporting for foreign-owned companies.

By Awais Jameel, Chartered Accountant. Reviewed by Muhammad Bilal, Chartered Accountant. Checked against official sources on . 3 minute read.

Short answer

Form 1120 is the federal income tax return for C corporations, including LLCs that elected to be taxed as corporations. The corporation reports its income and deductions and pays tax at a flat 21%. For calendar-year corporations it is due April 15, or October 15 with Form 7004. A corporation at least 25% foreign-owned also attaches Form 5472.

At a glance

Who files
C corporations, and LLCs that elected corporate tax treatment
Tax rate
21% of taxable income
Due
15th day of the 4th month: April 15, 2027 for calendar year 2026
Extension
Six months with Form 7004. It does not extend payment
Estimated tax
Required if the corporation expects to owe $500 or more
Foreign-owned 25% or more
Attach Form 5472 for each related party
Form 1120: the C corporation returnWho files: C corporations, and LLCs that elected corporate tax treatment; Tax rate: 21% of taxable income; Due: 15th day of the 4th month: April 15, 2027 for calendar year 2026; Extension: Six months with Form 7004. It does not extend payment; Estimated tax: Required if the corporation expects to owe $500 or more; Foreign-owned 25% or more: Attach Form 5472 for each related party.KEY FACTS AT A GLANCEForm 1120: the C corporation returnWho filesC corporations, and LLCsthat elected corporatetax treatmentTax rate21% of taxable incomeDue15th day of the 4thmonth: April 15, 2027 forcalendar year 2026ExtensionSix months with Form7004. It does not extendpaymentEstimated taxRequired if thecorporation expects toowe $500 or moreForeign-owned 25% or moreAttach Form 5472 for eachrelated partyChecked against official sourcesTax BakersForm 1120: the C corporation returnWho files: C corporations, and LLCs that elected corporate tax treatment; Tax rate: 21% of taxable income; Due: 15th day of the 4th month: April 15, 2027 for calendar year 2026; Extension: Six months with Form 7004. It does not extend payment; Estimated tax: Required if the corporation expects to owe $500 or more; Foreign-owned 25% or more: Attach Form 5472 for each related party.KEY FACTS AT A GLANCEForm 1120: the C corporationreturnWho filesC corporations, and LLCs that electedcorporate tax treatmentTax rate21% of taxable incomeDue15th day of the 4th month: April 15, 2027for calendar year 2026ExtensionSix months with Form 7004. It does notextend paymentEstimated taxRequired if the corporation expects to owe$500 or moreForeign-owned 25% or moreAttach Form 5472 for each related partyChecked against official sourcesTax Bakers
Key facts at a glance, as set out in this guide.

Who files Form 1120?

Every domestic corporation that has not elected S status files Form 1120, whether or not it had taxable income. For setting one up, see how to form a C corporation. That includes LLCs that elected to be taxed as corporations on Form 8832. A foreign-owned single-member LLC uses a pro forma Form 1120 only to carry Form 5472, which is a different exercise. See pro forma Form 1120.

When is it due?

By the 15th day of the 4th month after the tax year ends: April 15, 2027 for a calendar-year 2026 return. Form 7004 extends the filing date by six months, to October 15, 2027, but tax is still due by April 15. See Form 7004.

How is the return structured?

PartWhat it contains
Page 1, incomeGross receipts, returns, cost of goods sold from Form 1125-A, dividends, interest, rents and other income
Page 1, deductionsOfficer compensation, salaries, repairs, bad debts, rent, taxes, interest, depreciation, advertising, retirement plans, benefits and other deductions
Page 1, tax and paymentsTaxable income, total tax, estimated payments and amount owed or overpaid
Schedule CDividends received and the dividends-received deduction
Schedule JTax computation
Schedule KOther information, including ownership questions
Schedule LBalance sheet
Schedules M-1 and M-2Reconciliation of book income to taxable income, and retained earnings

Small corporations whose total receipts and total assets at year end are both under $250,000 generally do not need to complete Schedules L, M-1 and M-2, answering the relevant Schedule K question instead. Corporations with larger receipts file Form 1125-E to detail officer compensation.

How is the tax worked out?

Taxable income is gross income minus deductions, minus any net operating loss carried forward and special deductions such as the dividends-received deduction. The federal tax is 21% of taxable income. Credits reduce it. When the corporation later pays dividends, shareholders pay tax on them, which is the double taxation of C corporations. See how LLCs are taxed.

How tax on dividends adds a second layer is explained in C corp double taxation.

How are owners paid?

Owners who work in the business are paid salary through payroll, which is deductible. Dividends are paid from after-tax profit and reported to shareholders on Form 1099-DIV. Personal expenses paid by the corporation for owners can be treated as disguised dividends, so keep them out of the company accounts.

Does a corporation pay estimated tax?

Yes, if it expects to owe $500 or more. Calendar-year corporations pay on April 15, June 15, September 15 and December 15, electronically. Form 1120-W is used to work out the amounts, and Form 2220 calculates any underpayment penalty.

What if the corporation is foreign-owned?

A corporation with a foreign shareholder owning at least 25% must attach Form 5472 for each related party it had reportable transactions with. The penalty for not doing so is $25,000 per form. Dividends paid to foreign shareholders are generally subject to 30% US withholding, or a lower treaty rate, reported on Forms 1042 and 1042-S.

How is it filed?

Corporations that file 10 or more returns of any type during the year must file Form 1120 electronically. Others can e-file or mail it to the address in the instructions, which depends on the corporation's location and total assets.

To correct a filed return, see how to amend a business tax return.

Need your Form 1120 prepared?

We prepare Form 1120 and its schedules from your books, work out the tax and estimated payments, and attach any Form 5472 your ownership requires.

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Questions people ask

What is the tax rate on Form 1120?

A flat 21% of the corporation's taxable income.

When is Form 1120 due?

The 15th day of the 4th month after the tax year ends: April 15, 2027 for a calendar-year 2026 return, or October 15, 2027 with Form 7004.

Does an LLC ever file Form 1120?

Yes, if it elected to be taxed as a corporation. A foreign-owned single-member LLC also files a pro forma Form 1120 to carry Form 5472.

Do small corporations need a balance sheet on Form 1120?

Not if total receipts and total assets at year end are both under $250,000. They answer the relevant Schedule K question instead.

Sources

Every fee, date and rule on this page was taken from these official and primary sources.

  1. IRS: Instructions for Form 1120 (2025)
  2. Internal Revenue Code section 11: 21% corporate tax rate
  3. IRS: Form 1120-W, Estimated Tax for Corporations
  4. IRS: Instructions for Form 5472 (Rev. December 2024)

Rules and fees change. If you are reading this long after September 30, 2026, confirm the figures with the source before you rely on them.

Federal tax formsForm 7004: extending a business returnBusiness tax by entity typeHow LLCs are taxed: the four optionsStarting a US companyLLC vs S corp vs C corp: which one fits your business

More in Federal tax forms

Previous in this topicSchedule K-1 (Form 1065) explainedNext in this topicForm 1120-S: the S corporation returnTopicAll 33 guides in Federal tax forms

This guide is general information. It is not tax or legal advice for your situation.