For calendar-year C-Corporations, the federal tax filing deadline is April 15, 2026. Unlike pass-through entities where the penalty is a flat fee per owner, C-Corporation penalties are tied directly to the amount of unpaid tax.
The 2026 Late Filing Penalties for Form 1120
- The Standard Failure-to-File Penalty: The penalty is 5% of the unpaid tax due for each month (or partial month) the return is late. This penalty caps out at a maximum of 25% of the unpaid tax.
- The 60-Day Minimum Penalty (2026 Adjustment): If your corporate return is more than 60 days late, the IRS imposes a minimum penalty. For returns required to be filed in 2026, this minimum penalty is the smaller of $525 or 100% of the unpaid tax.
How to Fix It: IRS Penalty Relief
The IRS offers First-Time Penalty Abatement for businesses that have a clean compliance history for the preceding three tax years. Alternatively, if the delay was caused by a situation outside of your control, you can request relief under "Reasonable Cause".