California 1% Mental Health Tax: The 2026 Guide

The california 1% mental health tax applies to any individual, estate, or trust with California taxable income exceeding $1,000,000 in a given tax year. There is no blanket exemption for any category of taxpayer — not for retirees, not for trusts established before Proposition 63 passed, not for federally tax-exempt organizations that have taxable unrelated business income in California. If California taxable income crosses $1,000,000, the surcharge applies to every dollar above that threshold at exactly 1%.

The statute, codified at California Revenue and Taxation Code § 17043, defines the tax base as ‘California taxable income in excess of one million dollars ($1,000,000).’ There is no phase-out, no alternative minimum calculation, and no sunset. The threshold has been $1,000,000 since January 1, 2005, and has never been adjusted for inflation. In 2005 dollars, that $1 million threshold would be worth roughly $1,600,000 in 2026 dollars — meaning inflation has dragged more taxpayers into the surcharge every single year without any legislative action.

California residents owe the MHST on all income, wherever earned. A California resident who owns rental property in Texas, earns wages from a New York employer, and holds a New York City brokerage account owes California income tax — and potentially the MHST — on all of it. The source of income does not matter for residents; residency alone triggers worldwide taxation.

Nonresidents owe the MHST only on California-source income above $1,000,000. If a Texas resident owns a large apartment complex in Los Angeles and nets $1,400,000 of California-source rental income, the $400,000 above the threshold is subject to the 1% surcharge — $4,000 due on the nonresident return. Nonresidents must file Form 540NR and use the California-source income column to compute the MHST.

Estates and trusts are explicitly included in RTC § 17043. A California-resident trust (one administered in California or with a California fiduciary) owes the MHST on trust taxable income above $1,000,000. If income is distributed to beneficiaries and taxed at the beneficiary level, the MHST follows the income — the beneficiary owes it if their personal California taxable income exceeds the threshold. Careful trust distribution planning can sometimes split income across multiple lower-income beneficiaries to keep each below $1,000,000.

Common mistakes: some taxpayers incorrectly believe the MHST only applies to wage income or only to California-source income when they’re residents. Neither is correct. Others believe they can avoid the MHST by electing S corporation status and taking lower wages — but the MHST applies to the S corporation income that flows through to the shareholder’s California return, not just to wages. The distributable share is California taxable income just like wages.

One exemption that does technically exist: income that is constitutionally protected from California taxation. Military personnel stationed in California retain their home-state domicile under the Servicemembers Civil Relief Act, and wages for military service are not subject to California tax if the member is not a California domiciliary. If those wages were the primary income, the member might not owe the MHST even if stationed in California for the full year. This is a narrow exception and doesn’t apply to civilian income the member might earn on the side.

Where The Reed Corporation adds value here: we routinely identify clients who’ve been incorrectly computing California taxable income — either overstating it (and overpaying the MHST) or understating it (and facing FTB assessments with penalties and interest). A proper Schedule CA walkthrough, especially for clients with multi-state income, partnership interests, and stock compensation, is the foundation of accurate MHST computation. We also model whether a residency change is mathematically worth the disruption, given where income is actually sourced.

The California Pass-Through Entity Elective Tax (PTET), authorized under RTC § 19900 et seq. and enacted via AB 150 in 2021, lets qualifying partnerships, S corporations, and multi-member LLCs elect to pay a 9.3% entity-level tax on qualified net income. The electing owner then claims a dollar-for-dollar nonrefundable credit on their California personal return. The core purpose is to give high-earning pass-through owners a deductible state tax payment at the entity level, sidestepping the $10,000 federal SALT cap.

The PTET credit on Form 3804-CR reduces the owner’s regular California income tax computed on Form 540, line 15. It does not reduce the california 1% mental health tax on line 17. This is not a subtle distinction — it’s a fundamental limitation that many practitioners underestimate. The MHST is computed on California taxable income before applying credits, so even if the PTET credit wipes out all regular California income tax, the MHST survives intact.

Here’s the math: assume a single-member S corporation owner with $3,000,000 of California-source S corporation income. Regular California income tax at the top rate on income above the threshold: approximately $260,000. MHST: $20,000 (1% × $2,000,000 above the $1M threshold). If the S corporation makes the PTET election and pays the entity-level 9.3% on the $3,000,000 — that’s $279,000 — the owner gets a $279,000 credit against the $260,000 regular tax. The regular tax goes to zero, with a $19,000 carryover credit (the PTET credit is nonrefundable but carries forward). The MHST of $20,000 is still owed. Full stop.

The PTET election does, however, create a federal tax benefit that indirectly offsets the cost of the MHST. The entity-level PTET is deductible as a business expense at the federal level, reducing federal taxable income. For a top-bracket federal taxpayer at 37%, a $279,000 PTET payment generates approximately $103,000 of federal tax savings. When you net the $103,000 federal savings against the $20,000 MHST that wasn’t eliminated, the PTET election is still very favorable. The MHST is an additional cost on top of an otherwise beneficial strategy — not a reason to abandon the PTET.

What happens when income fluctuates? The PTET election is annual and irrevocable once made for that tax year (the election must be made by June 15 of the tax year and prepaid). If a year-end income estimate was too low and the PTET underpays relative to the actual distributable income, the credit may be less than expected. The MHST, meanwhile, will still be computed on actual California taxable income. Poor income estimates don’t reduce the MHST — they just mean the PTET benefit was smaller than planned.

The PTET does not change the MHST calculation in any other way — it doesn’t affect the $1,000,000 threshold, it doesn’t change the 1% rate, and it doesn’t affect the California taxable income base for MHST purposes. The entity-level election is invisible to the MHST computation; the income still shows up on the owner’s Schedule K-1 and flows to the California return as if no PTET election had been made.

A real-world documentation note: to claim the PTET credit, the owner needs FTB Form 3804-CR from the entity. The entity files Form 3804 to report the election and compute the credit. If the entity fails to file Form 3804 or misreports the qualified net income, the owner’s credit claim on their personal return can be disallowed — leaving them with regular California income tax that they thought was covered, plus the MHST they already knew they owed. Getting the entity-level paperwork right is not optional.

Where The Reed Corporation adds value: we handle both the entity-level PTET election filings and the corresponding credit claims on individual returns, and we model the interaction between the PTET federal deduction and the residual MHST cost. Our business management clients with complex pass-through structures often have multiple entities, some electing PTET and some not, and the aggregate California income picture needs to be tracked carefully to project MHST liability accurately for quarterly estimated payments.

Moving out of California can meaningfully reduce or eliminate exposure to the california 1% mental health tax — but only if the move is genuine, well-documented, and timed correctly relative to income events. California’s FTB is explicit that a change of domicile requires an intent to make the new state your permanent home, coupled with affirmative actions demonstrating that intent. Simply spending time in another state is not enough, and a high-income year is exactly when the FTB is most likely to scrutinize a claimed departure.

RTC § 17014 defines ‘resident’ to include anyone domiciled in California and any individual who is present in California for other than a temporary or transitory purpose. The second prong — ‘other than a temporary or transitory purpose’ — has been the basis for many FTB audit assessments against taxpayers who believed they had become nonresidents. FTB Publication 1031 outlines the factors: location of your home, spouse and children, social ties, professional licenses, business interests, and the location of personal property. No single factor is determinative.

For the MHST specifically, the stakes are high enough that a sloppily executed move can result in the FTB treating the taxpayer as a California resident for the entire year, not just the pre-departure months. In a year where a taxpayer has $4,000,000 of income, that’s $30,000 of MHST (1% × $3,000,000) — plus the regular California tax differential between resident and nonresident treatment on any non-California-source income.

Common mistakes in residency departures: (1) Keeping a California home after leaving, even as a vacation property — California treats continued home ownership as a strong indicator of domicile, though it’s not automatic. (2) Retaining a California driver’s license and voter registration. (3) Continuing to use California-licensed doctors, accountants, and attorneys as primary providers. (4) Having a business entity with ‘doing business’ status in California, which often means the owner is still filing Form 3522 (LLC fee) and Form 100S, tying them to the state economically. (5) Moving to Nevada, Texas, or Florida in Q4 of a high-income year — the FTB is deeply skeptical of end-of-year departures that perfectly coincide with IPOs, business sales, or large distributions.

The IRS and FTB both have income-matching programs. When a K-1 from a California partnership shows $1.5 million of California-source income flowing to a taxpayer who filed as a Nevada resident, that creates a mismatch. The FTB will send a Notice of Proposed Assessment under RTC § 19033 and require the taxpayer to substantiate the claimed nonresidency. The burden of proof in residency disputes effectively falls on the taxpayer.

Even genuine nonresidents can’t completely escape the MHST if they have California-source income above $1,000,000. A California real estate investor who moves to Nevada but retains a portfolio of California rental properties generating $2,000,000 annually will owe the MHST on $1,000,000 each year as a nonresident. The exit from California reduces the tax to just California-source income — it doesn’t eliminate the MHST on income that remains California-source by nature.

Practical documentation for a defensible residency departure: update driver’s license within 30-90 days of the claimed departure date (varies by state). Register to vote in the new state. Update all professional licenses or obtain reciprocal licenses in the new state. Establish new banking, brokerage, and insurance relationships in the new state. Document the date you stopped using California facilities as your primary home. Keep a day-count log — FTB auditors will ask for it. Some taxpayers use phone records, credit card statements, and GPS data to reconstruct presence. Having it proactively prepared is far better than reconstructing it during an audit.

Where The Reed Corporation adds value: we advise clients on the financial modeling of a genuine California departure — projecting the all-in MHST and regular California tax savings against the relocation costs, any California-source income that persists, and the compliance cost of the transition. We also prepare the part-year resident return (Form 540NR) for the year of departure, which requires careful allocation between the California-resident period and the nonresident period. Done wrong, the part-year return is a red flag; done right, it’s a clean and defensible filing.

Estimated tax payments for the california 1% mental health tax are not computed or remitted separately — they’re integrated into the regular California estimated tax payment system. When you make a California estimated payment using Form 540-ES, that payment covers both the regular income tax and the MHST. The FTB treats the entire California income tax liability, including the MHST, as a single obligation for purposes of the estimated payment rules under RTC § 19136.

The quarterly due dates for California estimated payments are April 15 (30% of the required annual payment), June 15 (40%), and January 15 of the following year (30%). Note there is no September 15 installment in California — the federal schedule has four equal installments, California’s schedule is 30/40/0/30. This difference catches many taxpayers, particularly those who assumed their tax advisor was managing California and federal estimates on the same calendar. Missing the June 15 payment or underpaying it triggers a penalty computed from June 15, not from the annual due date.

The required annual payment for penalty avoidance is the lesser of: (a) 90% of the current year’s tax (including MHST), or (b) 100% of the prior year’s tax — but only if the prior year California taxable income was $1,000,000 or less. If prior year California taxable income exceeded $1,000,000, the prior-year safe harbor requires 110% of the prior year’s California tax. This is a critical distinction from the federal rule, where the 110% threshold kicks in at $150,000 of AGI, not $1,000,000.

Example: In 2025, a California resident had $1,800,000 of California taxable income and paid $168,000 in California tax (including $8,000 of MHST). In 2026, the same taxpayer expects $3,000,000 of California taxable income and $280,000 of California tax (including $20,000 of MHST). Using the prior-year safe harbor at 110%: the required annual payment is $184,800 ($168,000 × 110%). The taxpayer can make four payments totaling $184,800 and avoid any underpayment penalty, even though the actual liability is $280,000. The $95,200 balance is due April 15, 2027, with interest accruing from January 15, 2027.

When income is lumpy — a business sale, an IPO, a carried interest distribution — the annualized income method under RTC § 19136(g) can be used to reduce or eliminate underpayment penalties. This method computes the required estimated payment for each installment based on actual year-to-date income through that period, rather than assuming income is earned evenly. If a taxpayer has minimal income through September and a massive gain in Q4, the annualized method shows low required payments for the first three installments and a large fourth installment — avoiding penalties on the first three installments that would otherwise be computed assuming uniform income.

Withholding from wages can reduce or eliminate the need for separate estimated payments. California income tax withheld on wages (and reported on W-2) is credited against the total California tax liability including the MHST. High-income employees who receive substantial bonuses may have enough withholding to cover their MHST without making separate estimated payments — but only if the withholding is sufficient. A W-2 employee earning $800,000 in wages with $1,400,000 in capital gains has minimal withholding on the capital gains and must make estimated payments to cover the MHST on the $1,200,000 of California taxable income above the threshold.

The California underpayment penalty rate is set quarterly by the FTB based on the federal short-term rate plus 3 percentage points under RTC § 19521. As of early 2026, this rate is approximately 7% annualized. On a $30,000 underpayment that starts accruing April 15 and is paid on April 15 of the following year, the penalty is approximately $2,100. Not catastrophic, but avoidable with proper planning. FTB Form 5805 must be filed with the return if the underpayment penalty applies; the FTB will also compute it independently and assess it if the form is not filed.

Where The Reed Corporation adds value: we project California estimated tax liability — including the MHST — on a quarterly basis for clients with variable income, particularly those with equity compensation, real estate sales, and pass-through entity distributions. We adjust estimates mid-year when income deviates from projections and ensure the prior-year safe harbor is properly applied. Many clients have unnecessarily overpaid quarterly estimates, essentially giving the FTB an interest-free loan, because their advisor defaulted to ‘pay the prior year amount’ without checking whether the 110% threshold applied and whether the current-year 90% method would result in lower required payments.

An FTB audit focused on the california 1% mental health tax usually arrives in one of two forms: a residency audit (the FTB believes you’re a California resident and so owe the MHST on worldwide income) or an income audit (the FTB believes your California taxable income is higher than reported, and so you owe more MHST). The documentation needed differs significantly between these two audit types, but both require organized, contemporaneous records — not reconstructed summaries.

For residency audits, the FTB will issue a questionnaire — typically the FTB Personal Income Tax Questionnaire — asking about your home addresses, days in California and outside California, location of your financial and professional relationships, and the location of your business interests. The gold standard documentation is a contemporaneous day-count log — a calendar or diary maintained in real time showing where you were each day. Many taxpayers reconstruct this from credit card statements, hotel receipts, airline boarding passes, and cell phone records. Reconstructed records are far weaker than contemporaneous records.

Supporting the day-count log: lease or deed for your home in the new state showing a move-in date before the claimed residency termination date; utility bills in your name in the new state; vehicle registration in the new state; bank and brokerage account change-of-address records; updated voter registration; professional license changes; and evidence that your primary physicians, dentists, and other service providers are in the new state. The FTB is looking for the totality of circumstances — no single document wins or loses the case, but a weak record across many factors loses.

For income audits — where the FTB is questioning the amount of California taxable income and so the MHST base — the key documents are: (1) All federal and California K-1s showing California-source allocations. (2) Partnership and S corporation tax returns (Forms 565, 100S) showing the California-source computation. (3) Documentation of federal-to-California basis differences that affect gain computations. (4) Records supporting California-specific deductions or addbacks on Schedule CA. (5) Trust agreements and trust accounting records if trust income is in question.

Stock compensation is a particularly audit-prone area. For employees with nonqualified stock options (NQSOs) or restricted stock units (RSUs), California taxes the compensation element based on the fraction of the vesting period spent in California under FTB’s ‘apportionment’ methodology. If you vested an option over four years, two of which were in California and two in another state, 50% of the spread on exercise is California-source income. The documentation needed: grant date, vesting schedule, percentage of days in California during the vesting period (the same day-count documentation as residency audits), and the exercise date. Without this, the FTB may treat 100% as California-source.

The FTB’s statute of limitations for assessment is generally four years from the due date of the return (or date filed, if later) under RTC § 19057. For substantial understatements — generally where omitted income exceeds 25% of gross income — the statute extends to six years. There is no statute for fraudulent returns. This means documentation needs to be retained for at least four years after filing, and ideally six years for returns with large capital gains or complex income items. The MHST, as part of the regular California income tax, is subject to the same statute of limitations.

What happens in an FTB audit: the FTB issues an audit notice under RTC § 19504, which begins a formal examination. The taxpayer has the right to representation — an attorney, CPA, or enrolled agent can represent you before the FTB under a valid Form 3520 (Power of Attorney). After the examination, the FTB issues a Notice of Proposed Assessment (NPA). The taxpayer can protest the NPA within 60 days, which initiates the protest process before the FTB’s Protest Office. If the protest is denied, the taxpayer can appeal to the Office of Tax Appeals (OTA). The OTA is an independent body and has in some cases overturned FTB residency determinations.

Where The Reed Corporation adds value: we’ve represented clients in FTB residency audits and income audits, including cases where the MHST was the primary disputed amount. We help clients organize their documentation before an audit begins, respond to FTB questionnaires without volunteering unnecessary information, and evaluate whether a protest or appeal is worth pursuing based on the strength of the record. Audit defense without experienced representation is a significant disadvantage — the FTB auditors are sophisticated and experienced with the arguments taxpayers commonly raise. Having a CPA firm that knows the FTB’s approach from the inside is a meaningful advantage.