2026 California State Tax Deadlines
California Individual income tax filing deadlines and extensions for 2026
If you are a resident or have been involved in business operations within California, you might be required to file California State taxes. California follows a progressive income tax structure with rates ranging from 1% to 13.3% (plus an additional 1% Mental Health Services Tax on income over $1 million), making it essential to understand the specific deadlines and requirements for 2026.
California business tax deadlines for 2026
C Corporations' deadlines and requirements
C Corporations in California must file and pay Corporate Income Taxes by April 15, 2027, following the federal due date schedule.
Filing requirements include:
- Complete Form 100 (California Corporation Franchise or Income Tax Return)
- File via CalFile or approved e-file software
- Payment must be made by April 15, 2027
- Mail submissions must be postmarked by the due date
Extension to file taxes in California for 2026
The Extension Deadline for California Corporate income tax returns is November 15, 2027. California automatically grants a seven-month extension following the federal extension timeline without requiring separate forms. This is an extension to FILE, not an extension to PAY—payment is still due April 15, 2027.
Pass-through entities
California S Corporations' tax deadlines for 2026
S Corporations must file in California by March 15, 2027.
Required forms include:
- Form 100S—S Corporation Franchise or Income Tax Return
California Partnerships tax deadlines for 2026
Partnerships must file in California by March 15, 2027.
Required forms include:
- Form 565—Partnership Return of Income
Extension to file S Corporations and Partnerships taxes in California for 2026
The Extension Deadline for both California S Corporations and Partnerships returns is September 15, 2027. California automatically grants a six-month extension without requiring separate applications. This is an extension to the FILE only—payments are still due March 15, 2027.
California Individual tax considerations for 2026
Filing requirements and income thresholds
California Individuals must file a State income tax return if their gross income exceeds specific thresholds based on filing status.
The progressive tax rates for 2026 range from:
- 1% on the first income bracket
- Up to 13.3% on income over $1 million (plus an additional 1% Mental Health Services Tax)
- Alternative Minimum Tax (AMT) may apply to high-income taxpayers
Estimated tax deadline for California 2026
Estimated tax payments are due on the following schedule for calendar year filers:
- April 15, 2026
- June 17, 2026 (extended due to holiday)
- September 15, 2026
- January 15, 2027
Who must make estimated payments
You must make California estimated income tax payments during 2026 if you expect to owe $500 or more in California income tax after subtracting withholding and credits. California has strict estimated tax requirements, especially for high-income taxpayers.
Individual tax deadline for California 2026
Individual income tax returns are due April 15, 2027.
Available forms include:
- Form 540—California Resident Income Tax Return
- Form 540NR—California Nonresident or Part-Year Resident Income Tax Return
- Form 540X—Amended Individual Income Tax Return
Extension to file taxes in California for 2026
The Extension Deadline is October 15, 2027, to file your California Individual Income tax return. California automatically grants a six-month extension without requiring separate extension forms. This is an extension to FILE, not an extension to PAY—payment is still due April 15, 2027.
What California tax professionals need to know
Several key considerations make California's tax landscape particularly complex for 2026. California has some of the highest state income tax rates in the nation, extensive compliance requirements, and unique provisions that differ significantly from federal tax law.
Electronic filing requirements
California has mandatory electronic filing requirements for many taxpayers:
- C Corporations and pass-through entities must file electronically in most cases
- Individuals can use CalFile for free electronic filing
- Professional preparers must use approved software vendors
- Large taxpayers have mandatory e-file requirements
LLC Annual Tax and Fee Requirements
California Limited Liability Companies face unique tax obligations:
- LLC Annual Tax of $800 minimum
- LLC Fee based on total income from California sources
- Graduated fee structure for LLCs with California-source income over $250,000
- Due dates vary, but generally follow partnership return schedules
California's unique tax features for 2026
Highest marginal income tax rates in the United States
California's progressive tax structure ranges from 1% to 13.3%, with an additional 1% Mental Health Services Tax on high earners.
Alternative Minimum Tax with different rules from the federal AMT
California maintains its own AMT system with regulations that differ from federal Alternative Minimum Tax calculations.
Mental Health Services Tax of 1% on income over $1 million
High-income taxpayers face an additional 1% tax on income exceeding $1 million to fund mental health services.
California conformity and non-conformity issues
California tax law differs significantly from federal tax law in many areas:
- Different depreciation rules and schedules
- Alternative treatment of certain business expenses
- Different rules for retirement account distributions
- Unique California tax credits and deductions
- Non-conformity with many recent federal tax law changes
High-income taxpayer considerations
California's progressive tax structure creates unique planning opportunities and challenges:
- Bunching strategies for deductions and income
- Multi-state tax planning for residents with income in other states
- Estimated tax planning to avoid underpayment penalties
- Alternative Minimum Tax planning and compliance
Professional tax guidance
Given California's complexity, consulting with qualified tax professionals through an accounting firm directory is especially important for California taxpayers to ensure compliance and optimize tax planning strategies.
Sources
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The material discussed on this page is meant for general illustration and/or informational purposes only and is not to be construed as investment, tax, or legal advice. You must exercise your own independent professional judgment, recognizing that advice should not be based on unreasonable factual or legal assumptions or unreasonably rely upon representations of the client or others. Further, any advice you provide in connection with tax return preparation must comply in full with the requirements of IRS Circular 230.
Please note that if any due date falls on a federal or state holiday or weekend, it may be adjusted to the next business day. Always verify current deadlines with the appropriate tax professional and authorities.
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