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California · 401k state-tax

401(k) and retirement accounts in California: state deduction and Roth considerations

Traditional 401(k) contributions reduce California taxable income today at 13.3% marginal. Roth 401(k) reverses the math. For equity earners, the state-tax dimension often flips the right answer.

What California residents actually pay

California taxes ordinary income at a top marginal rate of 13.3%. RSU settlement value, NSO exercise spread, and ESPP discount income all count as ordinary wages for this purpose and flow through the state's normal brackets.

Calculates its own state AMT; one of the most expensive states for ISO exercise.

Traditional 401(k) in California

A pre-tax 401(k) contribution reduces both federal and California taxable income today. At the top bracket, every $1,000 contributed saves 48.3 cents on the dollar (federal 35% + state 13.3%). At retirement, withdrawals are taxed at your then-current bracket.

Roth 401(k) breakeven

Roth 401(k) contributions are taxed at today's rates; withdrawals are tax-free. The Roth choice beats traditional when your retirement bracket is higher than your contribution bracket. For equity earners in high-income years, traditional is usually right during big RSU years and Roth is right during low-income transition years.

Mega-backdoor Roth

After-tax 401(k) contributions above the standard $23,500 limit can be converted to Roth in plans that allow it. For high earners in California, this is the largest tax-advantaged bucket available after the primary 401(k) and IRA caps. Check whether your plan allows after-tax contributions and in-plan Roth conversions.

Frequently asked

Does California tax RSU income the same as wages?
Yes. California treats RSU ordinary income as wages, taxable at the state's top marginal rate of 13.3%. Supplemental-wage federal withholding (22%, or 37% above $1M YTD) does not adjust for state withholding, so you often owe extra at filing.
What happens if I exercise ISOs while living in California?
California calculates its own AMT on top of federal AMT, so large ISO exercises can trigger two AMT bills. Plan the disqualifying-vs-qualifying disposition decision with both layers in mind.
I moved to California from another state. Who taxes my vesting RSUs?
Most high-tax states (CA, NY, MA) source RSU ordinary income to workdays between grant and vest. If your grant pre-dates your California move, expect the old state to tax the portion of each tranche attributable to workdays earned there. California taxes the remainder.
Can I reduce California taxes by timing my RSU sales?
California taxes long-term capital gains at the same rate as ordinary income, so timing alone does not produce a state savings — only federal. Holding for 12 months still halves the federal rate on gains above basis.

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