California C Corporation Tax Deadlines 2026
Complete guide to C Corporation filing dates, extensions, estimated payment schedules, and required forms in California for the 2026 tax year. California imposes a state income tax, so C Corporation entities must file both federal and state returns.
California C Corporation filing deadline
Automatic 7-month extension for most corporations in CA.
Due: Apr 15, 2026
Extension: Nov 15, 2026
Form: Form 100
Estimated payments
Quarterly estimated payment dates: Apr 15, 2026, Jun 15, 2026, Sep 15, 2026, Dec 15, 2026.
Due: Apr 15, 2026
California C Corporation Tax Calendar at a Glance
| Event | Date |
|---|---|
| Filing deadline | Apr 15, 2026 |
| Extension deadline | Nov 15, 2026 |
| Q1 estimated payment | Apr 15, 2026 |
| Q2 estimated payment | Jun 15, 2026 |
| Q3 estimated payment | Sep 15, 2026 |
| Q4 estimated payment | Dec 15, 2026 |
FAQ
When is the C Corporation tax filing deadline in California for 2026?
The California C Corporation tax return is due Apr 15, 2026 for the 2026 tax year. An extension is available until Nov 15, 2026.
Does California require C Corporation estimated tax payments?
Yes, California requires estimated tax payments for C Corporation entities. The quarterly due dates are: Apr 15, 2026, Jun 15, 2026, Sep 15, 2026, Dec 15, 2026. Penalties may apply if you underpay or miss a deadline.
What form do I file for a C Corporation in California?
C Corporation entities in California file using Form Form 100. You can download the form from California Franchise Tax Board at https://www.ftb.ca.gov.
Can I get an extension for my California C Corporation tax return?
Yes. California allows an extension for C Corporation returns until Nov 15, 2026. Note that an extension gives you more time to file, not more time to pay — any tax owed is still due by the original deadline of Apr 15, 2026.
What are the penalties for filing late in California?
California typically charges a failure-to-file penalty (usually 5% of unpaid tax per month, up to 25%) and a failure-to-pay penalty (usually 0.5-1% per month). Interest also accrues on unpaid balances. Filing for an extension by the original deadline avoids the failure-to-file penalty but not the failure-to-pay penalty.
Where can I file California C Corporation taxes?
File through California Franchise Tax Board. Visit https://www.ftb.ca.gov for e-filing options, downloadable forms, and payment portals.
California Estimated Tax Payments
View the full quarterly estimated payment schedule for California, including all entity types and payment methods.
View California estimated payments →