Married Filing Separately for Capital Gains in California: When It Helps

By Kevin Luu, Co-Founder and Chief Learning Officer. Reviewed on 2026-09-30.

For most high-income married couples in California, filing separately does not lower capital gains tax. The federal and California brackets for married filing separately are exactly half the joint brackets, and California’s community property rules split most of a couple’s income 50/50 on separate returns anyway. The one real benefit at incomes above $1 million is California’s 1% Behavioral Health Services Tax: on separate returns each spouse gets their own $1,000,000 threshold, which can save up to $10,000 a year.

This article walks through why the usual “keep one spouse in a lower bracket” idea does not work for a two-earner household, where the California surtax changes the math, what separate returns cost you, and how Washington families should think about it.

Why separate returns rarely change the capital gains rate

The old argument for filing separately was that it could keep one spouse’s gains in a lower bracket. For 2026, the numbers do not support that for a couple earning $750,000 or more. Under IRS Revenue Procedure 2025-32, every married-filing-separately breakpoint is half the joint one:

If the couple’s income divides evenly across two returns, the tax comes out the same as one joint return. If it divides unevenly, separate returns usually cost more, because the spouse with more income hits the 20% rate and the 37% bracket at half the joint threshold. For a family already well past $613,700 of taxable income, long-term gains are taxed at 20% plus the 3.8% Net Investment Income Tax either way (see the IRS NIIT page).

How community property splits income on separate returns in California

California and Washington are both community property states (IRS Publication 501). If you file separately, you do not simply report your own paycheck. Under IRS Publication 555, wages earned while married and living in a community property state are community income, and each spouse reports half. RSU income for work done during the marriage generally follows the same rule (a grant made before the wedding may be only partly community), and so do gains on shares bought or received with community earnings. The allocation is shown on Form 8958.

The exception is separate property: assets owned before the marriage, and gifts or inheritances to one spouse. In California and Washington, income from separate property stays separate income (Publication 555). That matters for capital gains, because a large gain on an inherited stock position would land entirely on the owning spouse’s separate return.

California also requires you to use the same filing status on your state return as on your federal return, except for registered domestic partners (FTB 2025 Form 540 booklet). You cannot file jointly for the IRS and separately for California.

Where California’s 1% surtax changes the answer

California taxes capital gains as ordinary income, with no lower rate (FTB). Its regular brackets for joint filers are also exactly double the single brackets used on separate returns, so the regular tax is neutral too. The Behavioral Health Services Tax is the exception. Under the 2025 Form 540 instructions (the latest published), it is 1% of taxable income over $1,000,000, and the threshold is the same $1,000,000 on a joint return as on each separate return. File separately with income split evenly, and the couple effectively gets $2,000,000 of room instead of $1,000,000.

Worked example: a San Mateo couple with an RSU sale

Assumptions (hypothetical, rounded): Priya earns $780,000 in W-2 pay including RSUs at a biotech company; Dan is an employed physician earning $420,000. In 2026 they sell RSU shares held more than a year for a $300,000 long-term gain. All of it is community property. After deductions, their California taxable income is $1,450,000. Two children, ages 4 and 7.

• Joint return, California surtax: 1% x ($1,450,000 – $1,000,000) = $4,500.
• Separate returns, California surtax: each spouse reports half, $725,000, which is under $1,000,000. Surtax: $0.
• Federal Net Investment Income Tax: joint, 3.8% x $300,000 = $11,400. Separate, each spouse has $150,000 of investment income and MAGI well above $125,000, so 3.8% x $150,000 = $5,700 each, $11,400 in total. No change.
• Federal Additional Medicare Tax: figured on each spouse’s own wages, even in a community property state (IRS Q&A). Both earn over the $125,000 separate threshold, so the total is 0.9% x ($1,200,000 – $250,000) = $8,550 either way.
• SALT deduction: $10,000 on the joint return (the $40,400 cap for 2026 phases down to the floor at this income). On separate returns each spouse is at the $5,000 floor, so the total is the same.

Net result in this example: separate returns save about $4,500 of California tax, before the extra preparation cost and the items in the next section.

How the saving scales with income

The difference tops out at $10,000 a year (1% of the second $1,000,000 threshold). A one-time liquidity event, such as selling a concentrated RSU position, is the year this most often comes up.

What filing separately costs a family with young children

• Child and dependent care credit. Married couples generally must file jointly to claim it (IRS Publication 503). The dependent care FSA still works: $3,750 per spouse on separate returns, $7,500 per household in total for 2026.
• Itemizing is all or nothing. If one spouse itemizes, the other cannot take the standard deduction (Publication 501).
• Capital losses. The deduction against ordinary income is $1,500 per separate return instead of $3,000 joint (IRS Topic 409). Community losses split evenly, but a loss on separate property helps only its owner.
• Roth IRA contributions. The direct-contribution phase-out for a spouse filing separately is $0 to $10,000 of MAGI (IRS Notice 2025-67). Most families at this income already use the backdoor route, so this rarely changes anything.
• Uneven separate-property gains. A large gain on inherited or pre-marriage shares stays on one return, where the 20% rate starts at $306,850 instead of $613,700 (2026). That can raise the tax.
• More work. Two returns, a community property allocation on Form 8958, and half of each spouse’s income tax withholding credited to the other.

There is one non-tax reason families choose separate returns: on a joint return both spouses are responsible, jointly and individually, for the full tax (Publication 501). If one spouse’s return has open questions, such as late K-1s or an unresolved equity grant, some couples prefer to keep the liability apart.

Washington: no state lever in 2026

Washington has no tax on wages in 2026 (WA DOR), so there is no state surtax to split. Its capital gains tax is 7% on long-term gains above the standard deduction, and 9.9% on taxable gains over $1,000,000. The standard deduction was $278,000 for 2025, and the Department of Revenue states it per individual, married couple or domestic partnership (WA DOR capital gains tax). Filing separately for the IRS does not give a married couple a second deduction. Real estate and retirement accounts are exempt.

That changes in 2028, when Washington adds a 9.9% income tax on AGI over $1,000,000. How married couples will be treated is still waiting on Department of Revenue guidance. Revisit the filing-status question once the rules are out.

How to decide, in order

1. Estimate your combined California taxable income for the year, including any planned stock sales. Under $1,000,000, the surtax gives no reason to file separately.
2. If you are above it, compare the surtax saving (up to $10,000) with what you would give up: the dependent care credit, any separate-property losses, and the extra preparation fees.
3. List every asset that is separate property. A big gain on one of them usually makes separate returns worse.
4. Remember the timing rule. You can generally switch from separate returns to a joint return within 3 years of the original due date (not counting extensions) by amending. Once you file jointly, you cannot switch to separate returns after the due date (Publication 501).

What to write down for your kids

Record which assets are community property and which are separate (the inheritance from a grandparent, the shares one of you owned before the wedding), and why you chose your filing status in a big sale year. That note does two jobs. It saves your tax preparer an afternoon every spring, and years from now it shows your children how you weighed a real trade-off instead of just leaving them a list of accounts. Conversations fade. Documentation compounds.

Common questions

Can a married couple file separately in California?

Yes. Either spouse can choose married filing separately. California requires you to use the same filing status as on your federal return, except for registered domestic partners. On separate returns, community property rules decide who reports what, so most wages and gains on community assets are split 50/50 between you.

Only one of us sold stock. Does filing separately put the gain on that spouse’s return?

Not in California if the shares are community property. Shares from RSUs earned during the marriage, or bought with earnings from that period, are generally community property no matter whose brokerage account holds them, so each spouse reports half the gain on a separate return. Only a gain on separate property, such as inherited shares or shares owned before the marriage, stays on the owner’s return.

If you are planning a large stock sale this year, our tax management team can run both filing statuses as part of the Tax & Wealth Assessment. Related reading: what happens if you file as single when married, taxes on a brokerage account you have not sold, ways to reduce MAGI, and our family governance work.

This is general education. The right filing status depends on your family’s full picture, so confirm it with your tax preparer before you file.

Written by

Kevin Luu

Co-Founder and Chief Learning Officer, Bright Advisers

Kevin has advised high-income W-2 tech and biotech families since 2015, and leads the education-first Age Five Family Office from Brea, California.

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