California Sole Proprietorship Tax Deadlines 2026
Complete guide to Sole Proprietorship filing dates, extensions, estimated payment schedules, and required forms in California for the 2026 tax year. California imposes a state income tax, so Sole Proprietorship entities must file both federal and state returns.
California Sole Proprietorship filing deadline
Sole proprietors file with personal return; automatic extension to file.
Due: Apr 15, 2026
Extension: Oct 15, 2026
Form: Form 540 / 540NR
Estimated payments
Quarterly estimated payment dates: Apr 15, 2026, Jun 15, 2026, Sep 15, 2026, Jan 15, 2027.
Due: Apr 15, 2026
California Sole Proprietorship Tax Calendar at a Glance
| Event | Date |
|---|---|
| Filing deadline | Apr 15, 2026 |
| Extension deadline | Oct 15, 2026 |
| Q1 estimated payment | Apr 15, 2026 |
| Q2 estimated payment | Jun 15, 2026 |
| Q3 estimated payment | Sep 15, 2026 |
| Q4 estimated payment | Jan 15, 2027 |
FAQ
When is the Sole Proprietorship tax filing deadline in California for 2026?
The California Sole Proprietorship tax return is due Apr 15, 2026 for the 2026 tax year. An extension is available until Oct 15, 2026.
Does California require Sole Proprietorship estimated tax payments?
Yes, California requires estimated tax payments for Sole Proprietorship entities. The quarterly due dates are: Apr 15, 2026, Jun 15, 2026, Sep 15, 2026, Jan 15, 2027. Penalties may apply if you underpay or miss a deadline.
What form do I file for a Sole Proprietorship in California?
Sole Proprietorship entities in California file using Form Form 540 / 540NR. You can download the form from California Franchise Tax Board at https://www.ftb.ca.gov.
Can I get an extension for my California Sole Proprietorship tax return?
Yes. California allows an extension for Sole Proprietorship returns until Oct 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 Sole Proprietorship 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 →