Home/Tax Center/Form 1120
IRS FORM 1120 · C-CORP RETURN

Your C-corporation reports its own income.

A C-corporation is a separate taxpayer. It files Form 1120 each year and pays federal income tax at the flat corporate rate on its own profit, before any dividends reach shareholders. We prepare and e-file the return from your financials, confirm your deadline, and flag the estimated payments that keep penalties away.

flat 21% corporate rate · e-file · accuracy verified July 2026
What Form 1120 is

The corporation is its own taxpayer.

Form 1120 is the annual federal income tax return for a C-corporation. Unlike a partnership or an S-corporation, a C-corporation does not pass its income through to owners for tax; it computes its own taxable income and pays federal income tax at the flat corporate rate on that profit. Shareholders are then taxed again on any dividends they receive, which is the double taxation people describe with C-corporations. The return reports income, deductions, credits, and the resulting tax, and it is filed every year the corporation exists, even in a year with no profit.

BosAI Tell me your fiscal year-end and whether you have paid estimated tax, and I will confirm your 1120 due date, your extended date, and whether an estimated payment is due so a penalty does not accrue. I help you file accurately; I do not give tax advice. Meet BosAI →
21%
flat federal corporate rate
1 return
filed every year the corp exists
6-month
extension via Form 7004
4.9/5
from 8,200+ founders

So what does the finished filing represent? Here it is.

What you file

A complete corporate return, e-filed from your books.

Form 1120 is built from your financial records: income, cost of goods sold, deductions, credits, and the schedules that support them. The result is a return showing the corporation's taxable income and the tax due at the corporate rate. Getting there accurately depends on clean books and the right supporting schedules, which is where most of the work is. We prepare the return from your financials, review it, e-file it, and store the acknowledgment, so you have a complete and defensible filing on record.

IRS FORM 1120 · CORPORATE INCOME TAX C-Corporation return
EntityC-corporation, calendar year
Tax computed atThe flat corporate rate on taxable income
Owners taxedAgain on dividends received
PREPARED · E-FILED
Acknowledgment stored in your vault · supporting schedules attached

Not every business files an 1120. Here is who does.

Who files it

C-corporations file 1120. Other structures file elsewhere.

Form 1120 is specifically the C-corporation return. Your tax structure determines whether it is the right form. Here is the line.

File Form 1120 if

  • You are a corporation taxed as a C-corporation, the default for a corporation.
  • Your LLC has elected to be taxed as a C-corporation.
  • The entity exists during the year, even with no income.
  • You have not made, or have revoked, an S-corporation election.

File a different return if

  • You have a valid S-election. That is Form 1120-S.
  • You are a multi-member LLC or partnership. That is Form 1065.
  • You are a single-member LLC with no corporate election. Report on the owner's return.
  • You are a tax-exempt nonprofit. That is the Form 990 series.

A common question: a C-corporation must still file Form 1120 for any year it exists, even if it had no activity or no profit. Skipping the return in a quiet year is a frequent and avoidable mistake, because the filing obligation follows the entity, not the income. We confirm your tax classification and filing obligation before the deadline so a dormant year does not turn into a missed return.

Right return for you? Here are the dates and penalties.

Deadlines and penalties

The corporate calendar is unforgiving.

These figures were verified against current IRS guidance. The ones that adjust each year are noted.

Form 1120 · deadlines, extensions, penalties ACCURACY VERIFIED · JULY 2026
Filing deadlineThe 15th day of the 4th month after the tax year ends. For a calendar-year corporation that is April 15. A C-corporation with a June 30 year-end has an earlier September due date.
ExtensionForm 7004 gives an automatic six-month extension, moving a calendar-year deadline to October 15. It must be filed by the original due date.
File vs payAn extension moves the filing date, not the payment date. Tax owed is due on the original date, and estimated taxes are generally paid quarterly during the year.
Late-file penaltyFive percent of the unpaid tax for each month the return is late, up to twenty-five percent. If the return is more than sixty days late, a minimum penalty applies, an amount the IRS adjusts annually.
Late-pay penaltyHalf a percent of the unpaid tax per month, up to twenty-five percent, plus interest, charged separately from the late-file penalty.
How to fileForm 1120 is e-filed, and many corporations are now required to file electronically. The corporate income tax rate is a flat twenty-one percent.

Dates in hand? Here is how the filing runs.

How filing works

From clean books to an accepted return.

The accuracy of an 1120 comes from the records behind it. Here is the sequence from financials to a filed return.

First · You and us

Assemble the financials

We start from your income statement, balance sheet, and records for the year, the basis for every figure on the return.

Prepared · Us

We prepare the return and schedules

We complete Form 1120 with the supporting schedules your situation requires, computing tax at the corporate rate.

Before the deadline · You

Review and pay

You review the return, and any tax due is paid by the original deadline so a late-payment penalty and interest do not start.

Filed · Us

We e-file and store the acknowledgment

We submit the return electronically, capture the IRS acknowledgment, and set next year's dates on your calendar.

The return is only as good as the records. Here is what we bring to it.

Why File.Business

Accurate, on time, and connected to the rest.

A corporate return is where accuracy matters most and where a missed estimated payment quietly adds up. The value here is a return prepared from clean records, filed on time, with the payment timing handled and the whole federal picture in one place.

Prepared to hold up

Right schedules, right tax

  • We build the return from your actual financials, not estimates.
  • We attach the supporting schedules your situation requires.
  • We flag estimated-payment timing so penalties do not accrue.
One federal record

Nothing filed in isolation

File Form 1120 →

Flat preparation fee shown up front. See what it costs →

The corporate return connects to a handful of related filings. Here is the road.

Related filings

The return sits in a wider federal picture.

The 1120 connects to your federal ID, your extension, your books, and the tax preparation behind it. They live on one platform, so the corporate return is one part of a coordinated whole.

EIN Extend File 1120 Books Prepare

Number it, extend it, file it, and keep the books behind it, all inside File.Business. One platform holds the corporate return and everything that feeds it.

BosAI Your 1120 dates are on my record, including the estimated-payment schedule. I remind you before each one and can pull the extension if the return needs more time. I assist with accuracy; I do not give tax advice.
Questions and references

The questions corporations ask about Form 1120.

When is Form 1120 due?

For a calendar-year C-corporation, Form 1120 is due on the 15th day of the fourth month after the tax year ends, which is April 15. Corporations with a fiscal year use the 15th day of the fourth month after their year-end instead, with a special earlier date for corporations whose year ends June 30. Filing Form 7004 by that date gives an automatic six-month extension, moving a calendar-year deadline to October 15. We confirm your exact dates based on your fiscal year.

Does a C-corporation pay tax, or do the owners?

The corporation pays. A C-corporation is a separate taxpayer that computes its own taxable income and pays federal income tax at the flat corporate rate. Shareholders are then taxed again on dividends they receive, which is the double taxation associated with C-corporations. This is the key difference from an S-corporation or partnership, where income passes through to owners and the entity itself generally pays no federal income tax.

Do I still file if the corporation had no income?

Yes. A C-corporation must file Form 1120 for every year it exists, even a year with no activity or no profit. The filing obligation follows the entity, not the income, so a quiet year still requires a return. Failing to file in a dormant year is a common and avoidable mistake. If the corporation is truly finished, the way to end the obligation is to formally dissolve it, not to simply stop filing.

What are the penalties for filing or paying late?

They are separate and can stack. The late-filing penalty is five percent of the unpaid tax for each month the return is late, up to twenty-five percent, with a minimum penalty if the return is more than sixty days late. The late-payment penalty is half a percent of the unpaid tax per month, up to twenty-five percent, plus interest. Because an extension moves only the filing date, paying by the original deadline is what avoids the payment penalty.

What are estimated taxes, and does my corporation owe them?

A C-corporation that expects to owe federal income tax generally pays it in quarterly estimated installments during the year, rather than all at once with the return. Underpaying those installments can bring its own penalty, separate from the late-filing and late-payment penalties on the return itself. Because the thresholds and due dates are specific, we look at your expected tax and flag whether estimated payments apply and when, so you are not caught short at filing time.

Can Form 1120 be e-filed?

Yes, and many corporations are now required to file electronically rather than on paper. E-filing returns an acknowledgment that the IRS received the return, which is useful proof of timely filing. We e-file wherever it is available, which is the standard path for corporate returns, and store the acknowledgment with your records. If your specific situation requires a different method, we handle that correctly.

What if I want to avoid double taxation?

Many small businesses elect S-corporation status precisely to avoid the corporate-level tax, so that income passes through to owners and is taxed once. That is a different return, Form 1120-S, and it requires a valid S-election. Whether the C-corporation or S-corporation path is better depends on your situation, including plans to raise investment, since some investors prefer C-corporations. We can help you understand the trade-off before you decide.

Start your business in the next 5 minutes.

No state-fee markup. Pay only the state fee. 60-day money-back guarantee.

No state-fee markup 60-day money-back Cancel anytime