Form 1120 — U.S. Corporation Income Tax Return — is required for all C‑corporations, and knowing the correct filing deadlines is essential to avoid late‐filing penalties and interest. Whether your corporation operates on a calendar year or a fiscal year, the IRS sets precise due dates. This detailed guide clarifies those deadlines and explains how to file for extensions using Form 7004.
📅 Default Filing Deadline for Calendar-Year C‑Corporations
If your corporation’s tax year aligns with the calendar year — ending December 31 — the standard Form 1120 due date is April 15 of the following year. For example:
- For the 2024 tax year, the return is due on April 15, 2025.
- If April 15 falls on a weekend or federal holiday, the deadline shifts to the next business day.
🗓️ Fiscal-Year C‑Corporations
If your corporation uses a fiscal year (for example, July 1 – June 30), the Form 1120 due date is the 15th day of the fourth month following the close of the fiscal year. For example:
- For the fiscal year ending June 30, 2025, the filing deadline is October 15, 2025.
- As always, if the 15th falls on a weekend or holiday, deadlines are extended to the next business day.
📝 Form 7004: Requesting an Extension
Form 7004 provides an automatic extension of time to file Form 1120, but not to pay taxes. Specifics include:
- A six-month extension is granted for calendar-year filers (moving April 15 to October 15).
- Fiscal-year filers receive a similar six-month window, e.g., October 15 to April 15 next year.
- Form 7004 must be submitted by the original due date — not after.
💰 Payments and Penalties to Avoid
Even with an extension, any tax owed must be paid by the original deadline to avoid—
- Failure-to-file penalty: 5% per month on unpaid tax, up to a maximum of 25%.
- Failure-to-pay penalty: 0.5% per month, up to 25%.
- Interest: Accrues daily from the original due date on unpaid tax.
🚦 Extension Timeline Summary
| Corporation Type | Tax Year End | Original Due Date | Extension Deadline (Form 7004) |
|---|---|---|---|
| Calendar‑year | Dec 31 | April 15, 2025 | October 15, 2025 |
| Fiscal‑year | June 30, 2025 | October 15, 2025 | April 15, 2026 |
🛡️ Special Situations to Monitor
- If your return is still processing from the prior year, file for extension and pay any estimated tax due.
- Corporations expecting losses should still file timely or request extension to preserve loss carryforward.
- Late processors should gather all financial statements promptly to reduce delays and penalty exposure.
🧭 Best Practices for Filing and Extensions
- Automate reminders: Use calendar alerts for both original deadlines and extension notices.
- Submit Form 7004 electronically: Get instant confirmation from IRS e‑file providers.
- Establish quarterly estimated payments: Maintain at least 90 % payment of current year or 100 % of prior year’s tax liability to avoid underpayment penalties.
- Track payment receipts: Retain EFTPS confirmation or bank statements for extension payments.
🔚 Final Takeaways
Whether your C‑corporation uses a calendar or fiscal year, understanding the Form 1120 deadlines and extension procedures in 2025 and 2026 is key to avoiding penalties and interest. File Form 7004 on time, pay estimated taxes promptly, and keep meticulous records. Proper planning prevents surprises and ensures your corporation remains compliant and in good standing.
