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What Is IRS Form 1120?

IRS Form 1120 is used by corporations to file their taxes. Specifically, to report their income, deductions, losses and gains, and credits. 


If you’re any type of U.S. corporation, Form 1120 (or some version of it) is the official IRS form you’d use to report your taxes. 

What is the difference between Form 1120 and 1120-S?

While Form 1120 is used by C corporations, Form 1120-S is specifically used by S corporations.

Before filing your taxes, make sure you have the correct version of Form 1120 for your corporation. 

Who Needs to File IRS Form 1120?

All corporations (unless exempt under Section 501), are required to file their tax returns using Form 1120. 

LLCs, however, don’t generally use Form 1120. 

Multi-member LLCs are typically treated as partnerships and must file Form 1065. 

Single-owner LLCs aren’t treated as a separate entity and report their income and deductions on their owner’s tax return. 

How to File IRS Form 1120: Step-by-Step Instructions


Form 1120 is one of the more complex IRS forms given it’s designed for corporate taxes.

However, there’s a good chance that much of it doesn’t apply to your business, so don’t be overwhelmed. 

It’s highly recommended to use a tax professional or at least software online to file your corporate taxes.

Not only to make sure that they’re accurate, but also just to get a little help (filling this out on your own can be time-consuming). 

With that said, let’s break down each section step-by-step:

1. Fill in your personal information

Straightforward, fill in your basic information including name, address, EIN, date incorporated, etc:

IRS FORM 1120 2

2. Fill in your income

Next, fill in your income breakdown: 

IRS FORM 1120 3

Make sure to add up the total on line 11 after adding all your information in. 

3. List out your deductions

Next, list out all of your deduction totals:

IRS FORM 1120 4

Again here, add up the total amount on line 27 as well. 

4. Credits and payments

Now, you’ll input all relevant credits or payments:

IRS FORM 1120 5

5. Sign and date

Finally, sign and date at the bottom:

IRS FORM 1120 6

Make sure to leave the section labeled, “Pair Preparer Use Only” blank as that is reserved only for when you pay a tax professional to prepare your tax return for you. 

Check out our guide on small business tax tips for additional tax filing tips.

Do I Need to Fill Out Schedule (C, J, K, L, M-1, M-2)?

Form 1120 has several additional sections included, those being schedules:

  • C
  • J
  • K
  • L
  • M-1
  • And M-2

Here’s how to know if you need to fill out one or more of these IRS Schedules: 

Schedule C

If you’re a solo business owner, there’s a chance you may have to fill out Schedule C.

Schedule C is designed for reporting earnings for individual business (usually sole proprietor) earnings. 

Learn more about Schedule C

Schedule J

Schedule J is designed for business owners who make a majority of their income through farming or fishing. 

Learn more about Schedule J. 

Schedule K

Schedule K is designed to report individual earnings or partnership income. If you’re in any kind of partnership, you may need to fill out Schedule K. 

Learn more about Schedule K.

Schedule L

If you’re a C corporation with total assets that exceed $10 million, you must file Schedule L along with your Form 1120. 

Learn more about Schedule L

Schedule M-1 and M-2

If your corporation’s gross receipts (or total assets) are greater than $250,000 at the end of the tax year then you typically need to complete Schedule M-1 (and possibly M-2) when filing.

Learn more about Schedule M-1

What Is the Deadline for Filing Form 1120?

Form 1120 is due on the 15th day of the 4th month after the end of the corporation’s tax year.

If your corporation uses a fiscal tax year ending June 30th, you’d file by the 15th day of the 3rd month after the end of your tax year. 

Can You File Electronically?

Yes, Form 1120 can be filed online or through mail.

However, make sure to check first to see if the software you’d like to use is authorized to e-file Form 1120 first. 

See this document for the approved list of software providers for e-filing: Publication 4163 (Rev. 12-2023)

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