Quick Answer
California's Mental Health Services Tax is a 1% additional state income tax on income over $1 million per year. For 2026, if you earn over $1 million, you pay 10.3% total state tax (9.3% regular rate + 1% MHST) on the excess. This affects about 45,000 California taxpayers annually and generates $2+ billion for mental health programs.
Best Answer
Sarah Chen, Payroll Tax Analyst
Best for California residents approaching or exceeding the $1 million income threshold who need to understand MHST calculations
What is the Mental Health Services Tax?
California's Mental Health Services Tax (MHST) is a 1% additional state income tax that applies to income over $1 million per year. Enacted by Proposition 63 in 2004, it's specifically designed to fund county mental health programs. The tax applies to all forms of income — wages, bonuses, capital gains, business income, and investment returns.
For 2026, the threshold remains at $1 million for all filing statuses (single, married filing jointly, married filing separately, head of household). This makes California unique, as most states that have millionaire taxes use different thresholds for different filing statuses.
How the tax calculation works
The MHST is calculated as 1% of your adjusted gross income (AGI) over $1 million. It's in addition to California's regular income tax, not instead of it.
Example 1: $1.2 million income
Example 2: $2 million income
Impact on different income types
Paycheck withholding implications
Many high earners first notice the MHST when they receive large bonuses or exercise stock options. California employers are required to withhold the additional 1% when they can reasonably expect your annual income to exceed $1 million.
Withholding example: If you earn $800,000 in base salary and receive a $400,000 bonus, your employer should withhold 10.3% California tax from the bonus ($41,200), not just the standard 9.3% ($37,200). The extra $4,000 represents MHST withholding on the $400,000 that pushes you over the $1M threshold.
Common misconceptions and planning mistakes
Myth 1: "The tax only applies to millionaires"
Reality: It applies to anyone with over $1M in income for that year, including one-time events like stock option exercises or business sales.
Myth 2: "It's a flat 1% tax rate"
Reality: It's 1% in addition to the regular 9.3% California rate, making the effective top rate 10.3%.
Myth 3: "I can avoid it by timing income"
Reality: While timing strategies can help, the tax applies to your total annual AGI, so deferring income just shifts the liability to future years.
Who pays the Mental Health Services Tax?
According to the California Franchise Tax Board, approximately 45,000 taxpayers pay the MHST annually, representing less than 0.3% of all California filers. However, this small group generates over $2 billion annually — about 15% of California's total income tax revenue.
Breakdown by income level (2024 data):
Strategic considerations for high earners
Timing large income events: If possible, spread large income events (stock option exercises, business sales) across multiple years to minimize MHST exposure.
Retirement account conversions: Roth IRA conversions that push you over $1M will trigger MHST, so plan conversion timing carefully.
Estimated tax payments: If your withholding doesn't account for MHST, you may need to make quarterly estimated payments to avoid underpayment penalties.
What you should do
1. Project your annual income: Use our paycheck calculator to estimate if you'll exceed $1 million
2. Review your withholding: Ensure your employer is withholding the additional 1% when appropriate
3. Plan estimated payments: High earners should make quarterly payments if withholding is insufficient
4. Consider timing strategies: Work with a tax professional to optimize the timing of large income events
5. Understand the permanence: Unlike federal tax cuts that expire, the MHST has no sunset provision
Key takeaway: California's Mental Health Services Tax adds 1% to your state tax rate on income over $1 million, affecting about 45,000 taxpayers annually and making California's effective top rate 10.3% — the highest in the nation.
Key Takeaway: California's Mental Health Services Tax adds 1% to your state tax rate on income over $1 million, making California's effective top rate 10.3% — the highest in the nation
California tax rates with and without Mental Health Services Tax
| Income Level | Regular CA Tax Rate | With MHST | Additional Tax on $100K |
|---|---|---|---|
| $500,000 | 9.3% | 9.3% | $0 |
| $1,100,000 | 9.3% | 10.3% on excess | $1,000 |
| $1,500,000 | 9.3% | 10.3% on excess | $5,000 |
| $2,000,000 | 9.3% | 10.3% on excess | $10,000 |
More Perspectives
Sarah Chen, Payroll Tax Analyst
Best for typical California employees who want to understand when this tax might affect them
When the Mental Health Services Tax affects regular employees
For most W-2 employees, the Mental Health Services Tax only becomes relevant in specific situations where your total annual income exceeds $1 million. This typically happens due to:
Real-world example: Tech employee
Sarah, a senior software engineer, earns $250,000 in base salary and receives $100,000 in annual bonuses. Normally, she wouldn't approach the $1M threshold. However, her company goes public and she exercises stock options worth $800,000.
Her employer should withhold this additional $1,500 when the stock options are exercised.
What to watch for on your pay stub
If you receive a large bonus or exercise stock options, look for "CA MHST" or "CA Mental Health" on your pay stub. Your employer should automatically withhold this if they project you'll exceed $1 million for the year.
Key takeaway: Most employees only encounter the Mental Health Services Tax during one-time events like stock option exercises or unusually large bonuses that push annual income over $1 million.
Key Takeaway: Most employees only encounter the Mental Health Services Tax during one-time events like stock option exercises or unusually large bonuses that push annual income over $1 million
Sarah Chen, Payroll Tax Analyst
Best for remote workers considering California tax implications or those who moved to/from California
MHST implications for remote workers and state changers
The Mental Health Services Tax creates unique complications for remote workers and people who change their California residency status during the year. The key question is whether you're considered a California resident for tax purposes.
California residency rules
California has aggressive residency rules. You're considered a California resident if:
Important: Even if you move out of California, you may still owe MHST on income earned while a California resident.
Common remote worker scenarios
Scenario 1: Left California mid-year
If you earned $1.2 million but only $600,000 while a California resident, you owe MHST on the California portion that exceeds $1M. The calculation is complex and often requires professional help.
Scenario 2: Working remotely for California company
If you live in Nevada but work remotely for a California company, you're generally NOT subject to MHST (California can't tax non-residents on income earned outside California). However, if you regularly work in California, different rules may apply.
Scenario 3: Stock options while changing residency
This is particularly complex. Stock options granted while a California resident may be subject to California tax (including MHST) even if exercised after moving to another state.
Key takeaway: Remote workers and those changing California residency face complex MHST calculations that depend on timing, residency status, and income source — often requiring professional tax guidance.
Key Takeaway: Remote workers and those changing California residency face complex MHST calculations that depend on timing, residency status, and income source — often requiring professional tax guidance
Sources
- California Revenue and Taxation Code Section 17043 — Mental Health Services Tax statutory requirements
- California FTB Publication 1001 — Supplemental Guidelines to California Adjustments
Related Questions
Reviewed by Sarah Chen, Payroll Tax Analyst on February 28, 2026
This content is for educational purposes only and is not a substitute for professional tax advice. Consult a qualified tax professional for advice specific to your situation.