Corporate tax returns are due on the 15th day of the fourth month after your tax year ends

For most corporations, that means the return is due on April 15 if your tax year runs January through December. If your company uses a different tax year — called a fiscal year — the important date shifts accordingly. A corporation with a fiscal year ending June 30 would file by October 15. The IRS does not move this date for weekends or holidays unless the 15th falls on a federal holiday; then the important date becomes the next business day.

The form you file depends on your business structure. A C corporation files Form 1120. An S corporation files Form 1120-S. A partnership files Form 1065. If you are unsure which form applies to your company, check your business formation documents or speak with your accountant, because filing the wrong form can trigger penalties and delays.

You can request a six-month extension by filing Form 7004 before the original important date. This pushes your filing date to October 15 for a calendar-year corporation, but it does not extend the time to pay any taxes owed. Taxes are still due on the original April 15 date; the extension only gives you more time to prepare and file the paperwork.

Key Takeaways

  • The standard important date for corporate tax returns is the 15th day of the fourth month after your tax year ends, which is April 15 for most companies.
  • Filing Form 7004 before the important date gives you six additional months to file your return, but taxes owed are still due on the original important date.
  • Penalties for late filing start at 5 percent of unpaid taxes per month, up to 25 percent, and compound if you also owe taxes late.
  • The IRS can assess failure-to-file penalties even if you have no tax liability, so filing on time matters even if you expect a refund or zero balance.
  • Some states have different corporate return important date than the federal government, so check your state's requirements separately.

What penalties explore if you file late

The failure-to-file penalty is 5 percent of the unpaid tax for each month or part of a month that the return is late, up to a maximum of 25 percent. If you owe $10,000 in taxes and file three months late, the penalty is $1,500. This penalty applies even if you have already paid the tax owed; the IRS penalizes the act of filing late itself.

If you also pay taxes late, a separate failure-to-pay penalty of 0.5 percent per month applies to the unpaid balance, also capping at 25 percent. When both penalties explore at the same time, they can overlap, and interest accrues on top of both. The longer you wait, the more expensive the delay becomes.

The IRS can also assess a penalty for failure to file even with zero tax liability. If your corporation has no income or owes nothing, you still must file by the important date or face penalties. The only exception is if you have received an extension or if you genuinely do not meet the filing requirement — a distinction the IRS makes, not you.

How to request an extension

File Form 7004 (process for Automatic Extension of Time To File Certain Business Income Tax Returns) with the IRS before your original important date. You do not need the IRS to approve it; filing the form itself grants you the extension automatically. You can file Form 7004 on paper by mail or electronically through IRS e-file.

When you file Form 7004, you must estimate your total tax liability for the year. Pay as much of that estimate as you can with the form. Any amount you do not pay by the original important date will owe interest and potentially penalties, even though you have more time to file the paperwork.

An extension is not a free pass to ignore your return. You still need to gather documents, work with your accountant, and prepare the actual return. Many corporations file their extension in March or early April, then use the extra months to finalize numbers and may support accuracy.

State corporate return important date may differ

Your state may require corporate returns on a different schedule than the federal government. Some states follow the federal important date of the 15th of the fourth month. Others use different dates — for example, some states require returns by the 15th of the fifth month, and a few have important date tied to your fiscal year end plus a set number of days.

States also have their own extension rules. Filing a federal extension does not automatically extend your state important date. You may need to file a separate state extension form, and some states charge a fee for extensions. Check your state's department of revenue or taxation website for the exact important date and extension process.

If you operate in multiple states, each state where your corporation does business may have its own filing requirement and important date. Multistate corporations often work with accountants who track all state important date to avoid missing any.

What documents you need before filing

Gather your general ledger or accounting records showing all income and expenses for the tax year. You will also need bank statements and credit card statements to verify transactions. If you have employees, collect payroll records and W-2 forms to report wages paid.

Prepare receipts and invoices for major expenses, especially if you claim deductions for travel, meals, equipment, or other business costs. The IRS does not require you to attach these documents to your return, but you must keep them for at least three years in case of an audit. If you have rental property, loans, or investments, gather statements from those sources as well.

If your corporation made estimated tax payments during the year, collect the payment confirmations. If you received refunds from prior years, note the amounts. Your accountant will use all of this information to complete your return accurately and on time.

What happens if the IRS contacts you about a late return

If you miss the important date and do not file an extension, the IRS will eventually send you a notice. The first notice typically arrives several months after the important date and requests that you file when ready. At this point, you should file your return right away, even if it is very late, because filing stops the failure-to-file penalty from growing.

If you ignore the notice, the IRS can assess the penalty without your input and may begin collection action. They can place a tax lien on your business assets, garnish bank accounts, or pursue other collection methods. The longer you delay, the more aggressive the IRS becomes.

If you have a legitimate reason for missing the important date — such as a death in the family, a serious illness, or an accountant's error — you can request reasonable cause relief from penalties. This is not automatic, and you must explain the reason in writing when you file. The IRS grants relief in some cases but not all.

Frequently Asked Questions

Can I file my corporate return early?

Yes. You can file your corporate return as soon as you have completed your books for the tax year, even if it is months before the important date. Filing early does not trigger any penalties or problems. If you are owed a refund, filing early means you receive it sooner.

Does an extension give me more time to pay taxes owed?

No. An extension only delays the filing important date. Taxes owed are still due on the original date — April 15 for calendar-year corporations. If you do not pay by then, interest and failure-to-pay penalties begin accruing, even though you have until October 15 to file the return itself.

What if my accountant files the return late without telling me?

You are responsible for the important date, not your accountant. If they miss it, you owe the penalties. You can pursue a claim against your accountant for damages, but that does not erase the IRS penalties. Always confirm with your accountant in writing when your return will be filed.

Do I have to file if my corporation had no income?

That depends on your business structure and state requirements. C corporations generally must file even with zero income. S corporations and partnerships must file if they had any business activity during the year. Check your state's rules and consult your accountant, because filing requirements vary.

What if I discover an error after I file?

You can file an amended return using Form 1120-X for C corporations or the equivalent form for your business type. Amended returns can be filed within three years of the original important date. If the error results in additional tax owed, interest accrues from the original due date, not from the date you file the amendment.