California Income Tax: 2026 Brackets, Rates & How CA Taxes Your RSUs and Stock Options

California has the highest state income tax rate in the country at 13.3%, and it treats equity compensation -- particularly ISOs -- differently than federal law. If you work in tech in California (and the majority of tech employees still do), understanding these rules is worth tens of thousands of dollars.

This guide covers the complete California income tax picture for 2026: brackets for all filing statuses, the Mental Health Services Tax, supplemental withholding rates, and the critical differences in how CA taxes RSUs, ISOs, and stock options.

California Income Tax Rates and Brackets (2025 Tax Year)

California uses a progressive tax system with 9 brackets plus the Mental Health Services Tax surcharge. Here are the current brackets:

Single / Married Filing Separately

Married Filing Jointly

California Standard Deduction (2025)

California's standard deductions are significantly lower than the federal amounts:

Compare that to the federal standard deduction of $15,000 (single) or $30,000 (MFJ) -- California gives you much less shelter. This means more of your income hits the CA brackets.

The Mental Health Services Tax

California's Mental Health Services Tax (MHST) adds an additional 1% on taxable income over $1,000,000. This applies regardless of filing status.

Key details:

• The $1M threshold is based on taxable income (after the standard deduction), not gross income
• It applies to ALL income types -- salary, RSU vesting, ISO exercises, capital gains
• Combined with the 12.3% top bracket, the effective top rate is 13.3%
• There is no marriage penalty -- the $1M threshold does not double for MFJ filers

For tech employees, reaching $1M in taxable income is more common than you'd think: a $250K salary plus $800K in RSU vesting in a single year puts you over the threshold. Large IPO vesting events, multi-year ISO exercises, or concentrated stock sales can all trigger the MHST.

Mental Health Tax Planning Example

Consider an employee with a $250K salary and $800K in RSU vesting in a single year:

By splitting the $800K RSU vesting across two years ($400K each), total taxable income stays below $1M in both years, avoiding the MHST entirely. For larger amounts, the savings scale: a $1.5M total income year triggers $5,000+ in MHST that could be avoided with timing.

California Supplemental Withholding Rate: 10.23%

When your RSUs vest, your employer withholds California state tax at the supplemental withholding rate of 10.23%. This is the flat rate California mandates for supplemental wages (bonuses, RSU vesting, stock option exercises).

Does 10.23% Match Your Actual Rate?

For most tech workers, 10.23% is close to their actual marginal rate:

• If you're in the 9.3% bracket ($72,724 -- $371,479 single), the employer over-withholds by roughly 1%
• If you're in the 10.3% bracket ($371,479 -- $445,771 single), it's approximately right
• If you're in the 11.3% or 12.3% bracket, the employer under-withholds, creating a state shortfall

Example: $100K RSU vest for someone in the 12.3% bracket

For high earners with large RSU grants, this shortfall compounds. $500K in RSU vesting at a 2% gap means $10,000+ in unexpected California taxes due at filing time.

How California Taxes RSUs

RSU taxation in California follows the same basic structure as federal: RSUs are taxed as ordinary income when they vest. The full fair market value on the vesting date is included in your W-2 and subject to California income tax.

The withholding flow:

1. RSUs vest and shares land in your account
2. Your employer sells a portion to cover taxes (sell-to-cover)
3. California supplemental withholding: 10.23% of the vesting value
4. You receive remaining shares after all tax withholding

The shortfall problem: Your employer withholds 10.23% for California, but your actual marginal rate may be 9.3%, 10.3%, 11.3%, 12.3%, or even 13.3%. Use our RSU Calculator to find your exact California withholding shortfall based on your total income and filing status.

For a complete walkthrough of how RSU withholding works at every level (federal, state, FICA), see our RSU tax withholding guide and our guide on how RSUs are taxed.

How California Taxes ISOs: The Critical Difference

This is the single most important state tax fact for anyone holding incentive stock options in California:

How this works in practice:

Suppose you exercise 10,000 ISOs with a $5 strike price and $25 FMV. The spread is $200,000.

This means a California ISO exercise creates both a federal AMT liability and a California ordinary income tax liability. The combined hit can be severe, and it's a major reason California tech employees need to plan ISO exercises carefully.

Use our ISO AMT Calculator to model both the federal AMT impact and the California state tax on your ISO exercise.

California State AMT (7%)

California is one of the few states with its own Alternative Minimum Tax. The California AMT rate is 7% of tentative minimum taxable income.

However, because California already taxes ISO exercises as ordinary income (not as an AMT preference item), the California AMT mainly affects taxpayers with large itemized deductions or other tax preference items -- not ISO exercises directly.

ISO Worked Example: Exercising 1,000 Shares in California

Suppose you exercise 1,000 ISOs with a $2 strike price and $10 FMV (spread of $8/share, $8,000 total). Here's how California treats this differently from other states:

A New York or Texas resident exercising the same ISOs would owe $0 in state tax at exercise. The California resident owes ~$744 immediately. For larger exercises -- say 10,000 shares at a $20 spread ($200,000) -- the California state tax alone is $18,600-$26,600, depending on your bracket.

This is why spreading ISO exercises across multiple years is especially important for California residents. Each year you exercise within a lower bracket saves thousands in state tax.

California Residency Rules for Equity Income

California's residency rules are aggressive when it comes to equity compensation. Understanding them is critical if you're considering a move out of state.

The safe harbor test: You're a California resident if you're present in the state for more than 9 months of the year. Below 9 months, California considers your domicile, family ties, and where your "closest connections" are.

Part-year sourcing of equity income: If you move out of California mid-year, your RSU vesting income is allocated between CA and your new state based on the ratio of work-days performed in each state. But there's a catch: RSUs granted while you were a California resident may be partially sourced to California even after you leave, based on the proportion of the vesting period spent in CA.

Equity sourced to CA after departure: California's FTB takes the position that if you earned equity compensation while performing services in California, the state can tax a portion of that income even after you move away. The formula is:

CA-sourced portion = (CA work-days during vesting period) / (Total work-days during vesting period)

This means moving from California to Texas on January 1st doesn't eliminate CA tax on RSUs that vest on March 15th if the vesting period included months of California employment.

Capital Gains in California

California does not offer a preferential tax rate for capital gains. Both short-term and long-term capital gains are taxed as ordinary income at your marginal rate (up to 13.3%).

This is a significant difference from the federal system, where long-term capital gains are taxed at 0%, 15%, or 20%. A California resident who sells appreciated stock pays up to 13.3% to California plus up to 20% (plus 3.8% NIIT) to the federal government -- a combined rate that can exceed 37%.

This matters for:

• Post-vesting RSU appreciation (selling RSU shares at a gain above the vesting price)
• ISO qualifying dispositions (selling after holding periods are met)
• Any stock or investment sales

Planning Tips for California Tech Employees

1. Spread ISO exercises across multiple years. Because California taxes ISO exercises as ordinary income, large exercises can push you into the 12.3% or 13.3% bracket. Exercising smaller batches each year keeps you in lower brackets and reduces both state and federal tax.

2. Track your supplemental withholding gap. If your total income puts you above the 10.3% bracket, your employer's 10.23% withholding isn't enough. Make estimated tax payments to avoid underpayment penalties.

3. Consider the Mental Health Tax threshold. If you're close to $1M in taxable income, timing equity events (RSU sales, ISO exercises) to stay below the threshold in a given year saves you 1% on every dollar above $1M.

4. Factor in the capital gains disadvantage. If you're holding appreciated stock, California's ordinary income treatment of capital gains means you pay more than residents of most other states on the same sale.

For a comparison across states, see our State Income Tax Guide. For federal tax planning, see the 2026 Federal Tax Brackets guide. For a detailed breakdown of effective tax rates at different income levels, see our RSU tax rate guide. If you hold early-stage equity, our 83(b) election guide covers the critical 30-day filing window.

Frequently Asked Questions

What is California's top income tax rate? California's top income tax rate is 13.3%, which includes the base top rate of 12.3% plus the 1% Mental Health Services Tax on taxable income over $1,000,000. This is the highest state income tax rate in the United States.

Does California tax RSU income? Yes. California taxes RSU vesting income as ordinary W-2 income at your marginal rate (up to 13.3%). Your employer withholds California tax at the supplemental rate of 10.23%, which may be more or less than your actual marginal rate depending on your total income.

How does California tax ISO exercises? California does not conform to the federal AMT treatment of ISOs. Instead, California taxes the spread on ISO exercises as ordinary income -- the same treatment as non-qualified stock options. This means California residents owe state income tax on ISO exercises that residents of most other states do not. This is the single most important state tax difference for ISO holders.

What is the California Mental Health Services Tax? The Mental Health Services Tax (MHST) is an additional 1% tax on taxable income exceeding $1,000,000. It applies regardless of filing status -- the $1M threshold does not double for married couples filing jointly. The tax applies to all income types including salary, RSU vesting, ISO exercises, and capital gains.

Can I avoid California tax by moving before my RSUs vest? Not entirely. California can source a portion of RSU income to the state based on the ratio of work-days performed in California during the vesting period. If you were granted RSUs while working in California, some of that income may be CA-taxable even if you move to another state before vesting. The earlier you move relative to your vesting dates, the smaller California's share.

Does California have AMT? Yes. California imposes a state-level Alternative Minimum Tax at a rate of 7%. However, because California already taxes ISO exercises as ordinary income rather than as an AMT preference item, the state AMT primarily affects taxpayers with large itemized deductions or other preference items -- not ISO exercises directly.