C-Corp Tax Return Due Date: When to File Form 1120 and What Happens If You Miss It

Описание: Learn the IRS due date for Form 1120 and what happens if you miss your C-Corp tax return deadline. Includes extension rules and penalties.

C-Corp Tax Return Due Date: When to File Form 1120 and What Happens If You Miss It

 

If you’re a startup founder running a Delaware C-Corp, your key IRS obligation is filing Form 1120, the corporate tax return. But when exactly is it due, and what happens if you miss the deadline? This guide breaks down the due date, extension rules, penalties, and how to avoid painful IRS consequences.

---

🧾 What Is the C-Corp Tax Return?

Form 1120 is the U.S. Corporation Income Tax Return, required for all C-Corporations, including startups.

This is how your business reports:

• Gross income

• Deductions

• Expenses

• Estimated payments

• Final tax due (or refund)

---

📅 When Is Form 1120 Due?

For most startups using a calendar fiscal year (Jan 1 – Dec 31), the due date is:

🗓️ April 15

If you use a fiscal year, it’s due the 15th day of the 4th month after your tax year ends.
So if your fiscal year ends on June 30, your Form 1120 is due October 15.

---

⏳ Can You File an Extension?

Yes, use Form 7004 to get a 6-month extension.

⚠️ But the extension only delays filing, not payment.
You must estimate and pay your taxes by April 15 to avoid penalties.

🔗 Learn more: Form 7004: How to File a C-Corp Tax Extension

---

💥 What Happens If You Miss the Deadline?

If you don’t file Form 1120 on time:

For startups, especially those with foreign ownership, missing the Form 1120 can also jeopardize your ability to:

• Raise capital

• Maintain Delaware compliance

• File Form 5472

---

🚀 First-Time Founders: What You Need to File

To hit the April 15 deadline, gather:

• EIN (Employer Identification Number)

• NAICS code (industry code)

• P&L + Balance Sheet

• Cap table + equity grants

• Details on any foreign transactions

Use this checklist to stay organized.

---

💻 How to File Form 1120

3 options:

1. Use an IRS-authorized e-file provider (TaxBandits, ProConnect, etc.)

2. Hire a CPA (recommended for funded startups)

3. Use TaxHero AI to file Form 1120 + Franchise Tax with AI assistance, deadline tracking, and reminders

---

📌 Quick Recap: C-Corp Tax Return Timeline

---

🔗 Related Posts to Help You File on Time

• Form 1120: Full Guide for Startups

• Form 7004 Extension Instructions

• Startup Tax Calendar 

• Delaware Franchise Tax: What’s Due by March 1

• Foreign Founder Filing: Form 5472 Explained

---

👋 Need Help Filing Form 1120?

TaxHero AI was built for startup founders:

• C-Corp deadline tracking

• AI-powered filing & reminders

• Handles Form 1120, 5472, Franchise Tax, and more

🎯 Start filing with TaxHero AI

 

Back to blogs