Tax Form 1120—What It Is, How to File It

By Ryan Smith on March 9, 2018

When you incorporate your business, you take on new responsibilities. One of these is filing Form 1120 (U.S. Corporate Income Tax Return)—five pages of dense text and empty, numbered boxes demanding to be filled.

Don’t let the fine print get you down. With a little preparation, Form 1120 is easily vanquished. Let’s look at who needs to file Form 1120, how to file it, and what business records you’ll need to have on hand to get the job done.

What is Form 1120?

Form 1120 is the tax form C corporations (and LLCs filing as corporations) use to file their income taxes.

Once you’ve completed Form 1120, you should have an idea of how much your corporation needs to pay in taxes. But that money doesn’t go to the IRS all in one lump sum; every corporation is required to pay quarterly estimated taxes.

What you need to file Form 1120

Whether you’re filing Form 1120 yourself, or your accountant is taking care of it, here’s a checklist of the information you should have on hand so you can complete and file the form.

  • Your Employer Information Number (EIN)
  • The date you incorporated
  • Total assets held by your corporation
  • Total income
  • Gross receipts
  • Cost of Goods Sold (COGS)
  • Dividends earned
  • Interest earned
  • Royalties earned
  • Capital gains
  • Tax deductions (These vary by company. There’s a wide range of tax deductions for businesses.)
  • Business tax credits you plan to apply for

How to file Form 1120

You have the option to file Form 1120 either online or by mail. Because it’s faster, easier, and cuts back on paperwork, we always recommend filing online using the IRS efile service.

Plus, some large C corporations reporting $10 million or more in assets are required to file online. Find out whether your C corporation has to file online.

When to file Form 1120

The deadline for filing Form 1120 for the 2017 financial year is April 17, 2018.


This post is to be used for informational purposes only and does not constitute legal, business, or tax advice. Each person should consult his or her own attorney, business advisor, or tax advisor with respect to matters referenced in this post. Bench assumes no liability for actions taken in reliance upon the information contained herein.

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Ryan Smith

Ryan writes for Bench, the online bookkeeping service that does your bookkeeping for you.