When Corporate Tax Returns Are Due

A corporate tax return (Form 1120 for C corporations, Form 1120-S for S corporations) is due on the 15th day of the fourth month after your tax year ends. For most businesses that use a calendar tax year (January 1 to December 31), that means the return is due April 15. If your business uses a different tax year — called a fiscal year — your deadline shifts accordingly.

The IRS will grant an automatic six-month extension if you file Form 7004 (Application for Automatic Extension of Time To File U.S. Individual Income Tax Return) before the original deadline. Filing for an extension moves your deadline to October 15 for calendar-year filers, but does not extend the time to pay any taxes owed. Taxes due are still calculated as of the original April 15 deadline, and interest accrues on unpaid amounts from that date forward.

Key Takeaways

  • Calendar-year corporations file Form 1120 or 1120-S by April 15; fiscal-year corporations file by the 15th of the fourth month after their tax year ends.
  • An automatic six-month extension (Form 7004) moves the filing deadline but not the payment deadline — taxes owed are still due by the original date.
  • Interest and penalties begin accruing on April 15 if taxes remain unpaid, even if you have filed for an extension.
  • S corporations, partnerships, and LLCs taxed as corporations each have their own form and sometimes different deadlines.

Different Deadlines by Business Structure

The deadline depends on what type of business entity you are. A C corporation files Form 1120 by April 15 (or the 15th of the fourth month after a fiscal year ends). An S corporation files Form 1120-S by the same date. A partnership files Form 1065 by March 15 (or the 15th of the third month after a fiscal year ends) — one month earlier than corporations. A limited liability company (LLC) taxed as a corporation follows the corporate deadline; an LLC taxed as a partnership follows the partnership deadline.

If you are unsure which form your business files, check your business registration documents or your prior-year tax return. The form number appears at the top of the first page. Your accountant or tax preparer can also confirm which deadline applies to you.

How the Extension Process Works

To request an extension, file Form 7004 with the IRS before your original deadline. You do not need a reason to receive the extension — it is automatic if you file the form on time. You can file Form 7004 electronically through tax software, by mail, or through a tax professional.

Filing an extension gives you six additional months to submit your return, but it does not reduce the amount of tax you owe or delay when that tax is due. If you expect to owe taxes, you should estimate the amount and pay it by the original deadline (April 15 for calendar-year filers) to avoid interest charges. The IRS charges interest on unpaid taxes from the original due date, regardless of whether you have filed an extension.

What Happens If You Miss the Deadline

If you do not file your return by the deadline and have not filed for an extension, the IRS will assess a failure-to-file penalty. This penalty is typically 5 percent of the unpaid tax for each month the return is late, up to 25 percent total. If you file more than 60 days late, there is a minimum penalty of $435 (as of 2024, though this amount may change yearly).

You will also owe failure-to-pay penalties and interest on any taxes that remain unpaid after the original due date. Interest is compounded daily and accrues from the due date until you pay in full. If you realize you will miss the deadline, filing for an extension and paying what you estimate you owe can significantly reduce these charges.

Fiscal-Year Filers and Special Situations

If your business operates on a fiscal year (any 12-month period other than January 1 to December 31), your deadline is the 15th of the fourth month after your fiscal year ends. For example, if your fiscal year runs July 1 to June 30, your return is due November 15. The same six-month extension is available — your extended deadline would be May 15.

Some businesses, such as those in certain industries or with specific ownership structures, may have different deadlines set by the IRS. Agricultural corporations, for instance, sometimes receive later deadlines. If you are unsure whether a special deadline applies to you, contact the IRS directly or consult a tax professional who knows your industry.

Paying Taxes Owed Alongside Your Return

When you file your return, you report the total tax your corporation owes for the year. If you have already paid estimated taxes throughout the year (through quarterly estimated tax payments), those payments are credited against your total liability. You then pay the remaining balance when you file.

You can pay by electronic funds withdrawal, credit or debit card, or check. The IRS website (irs.gov) lists all payment methods and their fees. If you cannot pay the full amount by the deadline, you can set up a payment plan with the IRS, though interest and penalties will continue to accrue until the balance is paid in full.

Frequently Asked Questions

What if my business closed during the year — do I still file a return?

Yes. You must file a final return for the year the business closed, reporting all income and expenses through the closing date. Mark the return as a "final return" in the appropriate box on the form. The same deadline applies unless you file for an extension.

Can I file my corporate return before January 1?

No. The IRS will not accept a corporate return for a calendar tax year before January 1 of the following year. If you need to file early, you can request permission from the IRS, but this is rarely granted. Most businesses file in February or March.

Do I have to pay estimated taxes if I file an extension?

An extension to file does not extend the time to pay. If you owe taxes, they are due by the original deadline (April 15 for calendar-year filers). Paying estimated taxes throughout the year or paying the full amount by the original deadline avoids interest and penalties.

What if I file late but pay on time?

You will still owe the failure-to-file penalty, which accrues from the original deadline. However, paying on time prevents the failure-to-pay penalty and interest from accumulating. The failure-to-file penalty is typically less costly than the combined failure-to-pay and interest charges.

How do I know if the IRS received my extension request?

If you file Form 7004 electronically, you will receive a confirmation number immediately. If you mail it, send it by certified mail with return receipt requested so you have proof of delivery. Keep a copy of the form and any confirmation for your records.