What's the exact federal tax on a $300,000 RSU vest in California?

At a typical $200k other-wage base, a $300,000 RSU vest adds approximately $103,484 of federal ordinary income tax, because the vest sits on top of existing wages and the marginal rate climbs through the brackets. The exact number depends on your other income, deductions, and filing status.

How much will California take?

California taxes the $300,000 vest as ordinary wage income at up to 13.3% at the top bracket. On this vest alone, that's approximately $39,900. The state stacks on top of the federal calculation.

What does my employer actually withhold?

Federal supplemental withholding is a flat 22% on the first $1M of supplemental wages per calendar year, then 37% above. On a $300,000 vest that's $66,000 in federal withholding. California state withholding at the top bracket is another $39,900. Medicare at 1.45% adds another $4,350.

Yes, by roughly $40,184. The 22% supplemental rate is below the marginal rate of a senior tech earner, and that gap compounds every vest. Cover it with a Q4 estimated payment or additional W-4 withholding before the next quarterly deadline.

How much tax on a $300,000 RSU vest in California?

How the number was derived

The calculation assumes a single filer with $200,000 of other wage income and no itemized deductions beyond the standard deduction. The RSU vest sits on top of that base, which is representative of senior IC tech earners. Federal tax uses 2025 single-filer brackets; California tax uses the top marginal rate of 13.3%; Medicare includes the 0.9% additional above $200k.

What changes if your numbers are different

A higher other-wage base shifts more of the vest into the top federal bracket (35-37%), raising your federal tax. A lower base produces a smaller average rate. Itemized deductions (SALT, mortgage interest, charitable) reduce the regular tax. If you have ISO exercises in the same year, AMT may apply and the arithmetic is different.

Frequently asked

What's the exact federal tax on a $300,000 RSU vest in California?: At a typical $200k other-wage base, a $300,000 RSU vest adds approximately $103,484 of federal ordinary income tax, because the vest sits on top of existing wages and the marginal rate climbs through the brackets. The exact number depends on your other income, deductions, and filing status.
How much will California take?: California taxes the $300,000 vest as ordinary wage income at up to 13.3% at the top bracket. On this vest alone, that's approximately $39,900. The state stacks on top of the federal calculation.
What does my employer actually withhold?: Federal supplemental withholding is a flat 22% on the first $1M of supplemental wages per calendar year, then 37% above. On a $300,000 vest that's $66,000 in federal withholding. California state withholding at the top bracket is another $39,900. Medicare at 1.45% adds another $4,350.
Am I under-withheld?: Yes, by roughly $40,184. The 22% supplemental rate is below the marginal rate of a senior tech earner, and that gap compounds every vest. Cover it with a Q4 estimated payment or additional W-4 withholding before the next quarterly deadline.

Educational estimate · 2025 brackets · Not tax advice · Single filer with $200k other wages

How the number was derived

What changes if your numbers are different

Frequently asked

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