Form 1120 Filing Deadline: Key Dates, Extensions, and Penalties for Corporations

Form 1120 is the annual corporate income tax return that every C corporation must file with the IRS to report your company’s income, expenses, and taxes owed. You must file it irrespective of whether or not you made a profit or not.

This filing is how the IRS enforces corporate tax compliance. If you skip it or miss the deadline, you could face monthly penalties, interest on unpaid taxes, and increased risk of an audit.

In this guide, we’ll help you with key due dates, extension rules, late filing penalties, and practical steps to stay compliant, especially if you’re managing deadlines without a full in-house finance team.

‍

Form 1120 Filing Deadlines for Corporations

Your filing deadline depends on your corporation’s accounting year and whether it’s a new or dissolved entity:-

i) Calendar-Year Corporations

If your corporation follows the calendar year (January 1 to December 31), your Form 1120 is due by April 15 of the following year. This is the most common setup for U.S. corporations.

ii) Fiscal-Year Corporations

If your fiscal year ends on a date other than December 31, you must file by the 15th day of the fourth month after your fiscal year ends. For instance, if your year ends June 30, the deadline is October 15.

iii) New and Dissolved Corporations

If your corporation started or shut down mid-year, you must file a short-year return. The deadline is still based on the 15th day of the fourth month after the short year closes, even if the business ran for only a few months.

Here’s a quick summary of the deadlines by corporation type:

Missing the right deadline, even by a few days, can trigger avoidable penalties. If you’re unsure which category your business falls into, speak with a tax advisor early or use our form 1120 filing solution that prompts the correct due date based on your setup.

‍

Extension Rules for Form 1120

If you're not ready to file Form 1120 by the deadline, the IRS gives you a way to buy time, without penalty if you act before the due date.

How to Request an Extension Using Form 7004

To get more time to file, submit IRS Form 7004 on or before your original filing deadline. This form grants an automatic six-month extension to file Form 1120. You don’t need to give a reason or wait for approval.

You can e-file Form 7004 through the IRS Modernized e-File (MeF) system or use any IRS-authorized e-filing provider. Make sure you include an estimate of your total tax liability, even if you expect to owe nothing.

Extension Deadlines and What’s Covered

The extension only gives you more time to file, not more time to pay. Any tax due must still be paid by your original Form 1120 deadline (e.g., April 15 for calendar-year corporations). If you underpay, interest and penalties will apply, even if you file the extended return on time.

In short, an extension protects you from late-filing penalties but not late-payment charges.

‍

Filing Deadlines for Other IRS Business Tax Forms

Form 1120 isn't the only tax filing that you need to manage. Depending on your payroll setup, business structure, and employee benefits, you may need to file several other IRS forms on different schedules.

Here's a breakdown of key forms and their electronic filing deadlines:

If you use payroll or accounting software, make sure it supports deadline alerts and automatic submissions for these forms. Otherwise, consider setting up calendar reminders or working with a professional to manage filings across the board.

‍

Penalties and Interest for Late Form 1120 Filing

Filing Form 1120 after the deadline can trigger monthly penalties and daily interest, even if your corporation owes little or no tax. These costs escalate the longer you delay.

i) Monthly Penalties for Late Filing

The IRS charges 5% of the unpaid tax for each month (or part of a month) that the return is late, up to a maximum of 25%.

If your return is over 60 days late, the minimum penalty is the lesser of $485 (for tax year 2024) or 100% of the unpaid tax.

For example, if your corporation owes $10,000 and files three months late, the penalty is:  5% of $10,000 × 3 months = $1,500

If you owe $0 but file 90 days late, the penalty is still $485.

ii) Interest and Penalties on Unpaid Taxes

Late payments attract two charges:

• 0.5% monthly penalty on unpaid tax
• Daily interest, calculated from the original due date until full payment is made

For example, if your corporation owes $20,000 and pays it 4 months late, you'll be charged:
0.5% of $20,000 × 4 months = $400 in penalties, plus interest, which varies based on federal rates.

These charges apply even if you filed for an extension. The extension only delays the paperwork, not the payment.

‍

How to Avoid Missing Corporate Tax Deadlines

Form 1120 filing is deadline-driven. If you don’t plan for it, penalties and errors are more likely. Here’s how you can stay ahead:

• Use tax software with built-in deadline tracking - Choose platforms that send reminders and support e-filing for Form 1120 and extensions.
  
  
• Set calendar reminders well in advance - Give yourself enough time to collect documents, review details, and complete the return.
  
  
• Work with a CPA or tax advisor - A professional can help you stay accurate, claim eligible deductions, and file on time.
  
  
• Avoid last-minute submissions - Early filing helps you avoid errors, submission delays, and missed deductions.

Also track due dates for payroll and information returns. A shared tax calendar makes it easier to manage all obligations in one place.

‍

File Early and Stay Compliant

Form 1120 is a legal requirement for every C corporation operating in the U.S. Missing the deadline can lead to penalties, interest, and compliance issues that grow over time.

Knowing when and how to file helps you reduce risk, avoid unnecessary costs, and stay focused on running your business.

If you want help managing tax deadlines and extensions, reach out to us. Book a demo to see how Inkle helps corporations stay compliant with IRS filing requirements.

‍

Frequently Asked Questions

1. When is Form 1120 due for corporations that follow a calendar year?

If your corporation’s tax year ends on December 31, Form 1120 is due by April 15 of the following year.

2. What is the Form 1120 deadline for corporations with a fiscal year-end?

The deadline is the 15th day of the fourth month after your fiscal year ends. For example, if your year ends on June 30, your return is due October 15.

3. How can a corporation request more time to file Form 1120?

File Form 7004 on or before your Form 1120 due date. It gives you an automatic six-month extension to file.

4. What penalties apply if a corporation files Form 1120 late?

The IRS may charge a 5% monthly penalty on unpaid tax, up to 25%, plus a minimum penalty of $485 if the return is over 60 days late.

5. Are there additional charges if a corporation pays taxes late?

Yes. The IRS applies a 0.5% monthly penalty on unpaid tax and daily interest until the full amount is paid.