California Bonus Tax Rate: How to Calculate the 10.23% Supplemental Method

What Is the California Bonus Tax Rate?

California's bonus tax rate is 10.23%. When your employer pays a bonus or exercises stock options on your behalf, they withhold 10.23% of the gross amount for California state income tax. On a $5,000 bonus, that means $511.50 withheld before you ever see the money.

This rate applies to bonuses and stock options paid on or after November 1, 2009, as established by the California Employment Development Department (EDD). A separate, lower rate of 6.6% applies to other supplemental wages — commissions, overtime pay, severance, and vacation pay — that are not bonuses or equity compensation.

Supplemental Wages Explained

The California EDD defines supplemental wages as compensation paid in addition to an employee's regular wages. The category matters because the withholding rate varies by the type of supplemental payment — and employers frequently apply the wrong rate, creating either over- or under-withholding problems for employees.

How to Calculate the 10.23% California Bonus Tax

When a bonus is paid as a separate check — separate from your regular paycheck — the calculation is simple and uses a single flat formula.

The Formula

California bonus withholding = Bonus amount × 0.1023

No allowances. No bracket lookup. The 10.23% rate applies to the full gross bonus regardless of your income level or how many exemptions you claimed on your DE 4.

Step-by-Step Walkthrough

1. Identify your gross bonus — the full amount before any deductions.
2. Multiply by 0.1023 — California state income tax withholding.
3. Multiply by 0.22 — federal income tax withholding (for bonuses up to $1 million).
4. Multiply by 0.062 — Social Security (OASDI), up to the annual wage base.
5. Multiply by 0.0145 — Medicare (add 0.009 if your YTD income exceeds $200,000).
6. Apply the current California SDI rate — verify the current year's rate with the EDD, as rates and wage base rules have changed in recent years.
7. Subtract all withholdings from the gross bonus to find your net take-home.

Totals exclude SDI (verify current year rate with EDD). Assumes Social Security wage base not yet reached. Amounts are rounded.

Federal vs. State: The Complete Tax Picture

When people say their bonus was "taxed at 40%," they are almost always describing the sum of every withholding — federal, state, and payroll taxes — not a single 40% rate. Here is exactly what each layer costs you.

Federal Bonus Withholding

The IRS requires a 22% flat withholding rate on supplemental wages up to $1 million in a calendar year. Bonuses that push your total supplemental wages above $1 million in that year are subject to a 37% rate on the excess amount.

Total Withholding Breakdown for California Employees

• Federal income tax: 22% (37% on the portion above $1M in supplemental wages)
• California income tax: 10.23% (bonuses and stock options)
• Social Security (OASDI): 6.2% up to the annual wage base (verify current year limit)
• Medicare: 1.45% on all wages
• Additional Medicare Tax: 0.9% on wages above $200,000
• California SDI: Verify current year rate at edd.ca.gov (wage cap removed as of 2024)

Percentage Method vs. Aggregate Method

California employers can choose between two methods for withholding state tax on bonuses. Most employees only discover the distinction exists when their take-home is far lower than expected.

Percentage Method (Flat Rate)

When a bonus is paid on a separate check, the employer applies the flat 10.23% rate directly to the bonus amount. The calculation is straightforward, the withholding is predictable, and employees are rarely surprised by the result.

Aggregate Method (Combined Wages)

When a bonus appears in the same paycheck as regular wages, the employer must (or may) use the aggregate method. Here is how it works in practice:

1. The bonus is added to the regular wages for that pay period.
2. The standard California withholding tables are applied to the combined total.
3. The withholding already deducted from the regular wages is subtracted.
4. The remainder is withheld from the bonus.

Because the combined amount is treated as if it were a single regular paycheck at that elevated amount, it falls into a higher withholding bracket — producing significantly more withholding than the flat 10.23% method.

Concrete Example: $10,000 Bonus Combined With an $8,000 Paycheck

Assume a single filer with no DE 4 allowances. Regular biweekly wages: $8,000. Bonus paid in the same check: $10,000. Combined: $18,000.

• Under the percentage method on the $10,000 bonus alone: California withholding ≈ $1,023.
• Under the aggregate method on $18,000 combined: the withholding table rate at that income level is substantially higher, producing California withholding on the bonus portion of approximately $1,600–$2,200 depending on annualized income and the applicable bracket.
• That is $600–$1,200 more in California withholding for the same $10,000 bonus, simply because of how the paycheck was structured.

The aggregate withholding is not a permanent loss — it is credited toward your annual liability and generates a larger refund if you overpaid. But the immediate cash flow impact is real.

Real-World Scenarios

The following examples reflect situations California workers commonly encounter. Each shows the full withholding breakdown so you know exactly what to expect.

Scenario 1: $5,000 Performance Bonus, Separate Check

Situation: You receive a $5,000 annual performance bonus paid as a separate check.

• California tax: $5,000 × 0.1023 = $511.50
• Federal tax: $5,000 × 0.22 = $1,100.00
• Social Security: $5,000 × 0.062 = $310.00
• Medicare: $5,000 × 0.0145 = $72.50
• CA SDI: Verify current rate with EDD
• Total withholding (excl. SDI): approximately $1,994
• Net take-home (excl. SDI): approximately $3,006

Scenario 2: $10,000 Signing Bonus, Aggregate Method

Situation: You receive a $10,000 signing bonus in the same paycheck as your regular $8,000 biweekly salary. Your employer uses the aggregate method.

Your employer treats the combined $18,000 as a single biweekly paycheck, consults the California withholding tables, and then subtracts what would have been withheld on your $8,000 alone. The result: California withholding on the bonus portion of approximately $1,600–$2,200 — compared to the $1,023 you would have had under the flat percentage method. The difference of $600–$1,200 is not taxed away permanently; it is prepaid toward your annual California liability and will increase your refund (or reduce the amount you owe) when you file.

Scenario 3: $50,000 RSU Vesting

Situation: 500 RSUs vest at $100 per share, creating $50,000 of ordinary income.

• California tax: $50,000 × 0.1023 = $5,115.00
• Federal tax: $50,000 × 0.22 = $11,000.00
• Social Security: $50,000 × 0.062 = $3,100.00
• Medicare: $50,000 × 0.0145 = $725.00
• CA SDI: Verify current rate with EDD
• Total withholding (excl. SDI): approximately $19,940
• Net value after withholding (excl. SDI): approximately $30,060

For employees whose total compensation exceeds $200,000, the Additional Medicare Tax (0.9%) kicks in, and for those earning over $1 million, California's 13.3% top marginal rate means the 10.23% withholding will be insufficient. Such earners should expect to owe additional California tax at filing and may need to make estimated payments. See the year-end section for details.

Special Cases & Edge Cases

Stock Options and RSUs

Both non-qualified stock options (NQSOs) and RSUs generate ordinary income subject to the 10.23% California withholding rate at the time of exercise or vesting. Incentive stock options (ISOs) have different rules: there is no regular income tax withholding at exercise (though the spread may trigger AMT), but California does not conform to the federal ISO exemption for AMT purposes.

• California's top marginal tax rate is 13.3% for income over $1 million. High earners will owe the difference between the 10.23% withheld and their actual 13.3% rate when they file.
• Combined with federal (37% over $1M), Additional Medicare (0.9%), and SDI, total withholding and tax on equity compensation for the highest earners can exceed 52%.
• For ISOs triggering AMT, a separate California AMT calculation is required — consult a tax professional.

All Types of Cash Bonuses Qualify for 10.23%

The type of bonus does not change the rate. Signing bonuses, performance bonuses, retention bonuses, discretionary bonuses, spot bonuses, and holiday bonuses are all subject to the same 10.23% California withholding when paid separately from regular wages. The label assigned to the bonus by the employer has no tax significance.

Moving Expense Reimbursements

Since 2018, most employer-paid moving expense reimbursements are taxable to the employee under federal law. These payments are classified as supplemental wages and are subject to the 6.6% California withholding rate — not the 10.23% rate that applies to bonuses.

Residency & Remote Work Rules

Where California taxes you depends on where you live and where you performed the work — not where your employer is headquartered. This distinction creates real implications for remote workers and anyone who has relocated.

California Residents

California residents are taxed on all income from any source, including bonuses paid by out-of-state employers for work performed outside California. If you live in California, the 10.23% withholding applies regardless of where your employer is located.

Nonresidents

Nonresidents owe California tax only on California-source income. For a bonus, the key question is: where were the services performed that earned the bonus?

• Services performed in California → bonus is California-source income → 10.23% withholding applies.
• Services performed entirely outside California → bonus is generally not California-source income → no California withholding required.
• Services performed partly in California and partly elsewhere → the bonus must be apportioned; only the California-earned portion is subject to California tax.

Part-Year Residents

If you moved into or out of California during the tax year, you file Form 540NR and allocate income between the California-resident and non-resident periods. Bonuses paid after you left California for work you performed before leaving are still California-source income — the timing of the payment does not determine the source.

Remote Workers Living Outside California

If you live in Nevada, Oregon, Washington, or any other state and work remotely for a California company without physically entering California:

• Your wages — including bonuses — are generally not California-source income if all work is performed outside California.
• Many California employers still withhold California tax by default. File a California nonresident return (Form 540NR) to claim a refund.
• If you occasionally travel to California for work (meetings, conferences), the days spent working in California may create a partial California tax obligation through day-counting apportionment.

Employer Responsibilities & Compliance

California takes payroll tax compliance seriously. Employers who incorrectly withhold — or fail to withhold at all — face penalties, interest, and in some cases direct liability for the tax owed by the employee.

Withholding Requirements

• Withhold 10.23% on bonuses and stock options paid separately from regular wages.
• Withhold 6.6% on commissions, overtime, severance, vacation pay, and other supplemental wages.
• Use the aggregate method when supplemental wages are included in the same check as regular wages.
• Apply the current SDI rate — verify annually with the EDD, as the rate can change year to year.

Reporting Requirements

• Form W-2: Bonuses are included in Box 1 (federal wages) and Box 16 (California state wages).
• DE 9C: Quarterly Contribution Return and Report of Wages — filed with the EDD.
• DE 88: Payroll tax deposit — timing depends on your deposit schedule (quarterly, monthly, semi-weekly, or next-day for large deposits).

Penalties for Non-Compliance

• Failure to withhold: Penalty up to 20% of the tax that should have been withheld.
• Failure to deposit on time: Graduated penalties from 2% to 10%, depending on how late the deposit is.
• Interest: Accrues on all unpaid balances.
• Personal liability: If the employer fails to remit and the employee cannot pay, the EDD can pursue the employer — and in some cases the responsible officers — for the tax owed.

Year-End: Withholding vs. Actual Tax Liability

Every dollar withheld from your bonus is a prepayment toward your annual tax liability — not a final tax determination. What you actually owe (or get back) is settled at tax filing. This distinction matters more for bonus recipients than for anyone else, because the flat 10.23% withholding rate rarely matches the employee's true marginal rate exactly.

When You Will Likely Get a Refund

• Your total annual income falls below California's higher tax brackets — your actual rate is less than 10.23%.
• Your employer used the aggregate method, producing more withholding than necessary.
• You have deductions (mortgage interest, significant charitable contributions, business expenses) or credits (child tax credit, earned income credit) that reduce your taxable income.
• You changed jobs mid-year and had a gap in income, keeping your annual total lower than expected.

When You May Owe Additional Tax

• Your total income pushes you into California's 11.3%, 12.3%, or 13.3% brackets — above the 10.23% withheld.
• You have additional income sources (rental income, freelance work, investment gains) that were not subject to withholding.
• You are subject to the Net Investment Income Tax (3.8%) or the Alternative Minimum Tax at the federal level.
• Your RSUs or stock option exercises created large ordinary income that the flat 10.23% withholding cannot fully cover.

Estimated Tax Payments

If you expect to owe more than $500 in California income tax (above withholding) or more than $1,000 federally, you should make quarterly estimated tax payments to avoid underpayment penalties.

Note: California's Q1 payment is due April 15, not an earlier date. If the due date falls on a weekend or holiday, it shifts to the next business day. Always confirm dates at ftb.ca.gov.

Bonus Timing Strategies

The calendar year in which you receive a bonus determines which year's tax rates and brackets apply. In most cases you cannot control this — but in some situations you can, and the difference in net take-home can be significant.

Deferring a Bonus to a Lower-Income Year

If you know that next year's income will be substantially lower — because you plan to retire, reduce hours, take parental leave, or leave a high-paying job — receiving a bonus in that lower-income year can reduce your actual tax liability even if the withholding rate remains 10.23%.

Some employers allow employees to defer the payment of a discretionary bonus. This must be structured under Section 409A deferred compensation rules to avoid severe tax penalties. Informal arrangements ("just pay me in January") can create tax problems if the employer already determined the amount and you had a legal right to it in the prior year.

Accelerating a Bonus Into the Current Year

Conversely, if you expect significantly higher income next year — a large equity vesting event, a promotion, or a business sale — receiving a bonus now, in a lower-income year, may reduce your total tax cost.

Relocating Before a Large Bonus or Vesting Event

Some employees who plan to leave California attempt to time large RSU vesting events or bonus payments to occur after they have established residency in a no-income-tax state. California's aggressive sourcing rules make this complicated: if the equity was granted while you were a California resident or employee, California generally claims a portion of the income proportional to the time you spent in California during the vesting period.

California vs. Other States

California's 10.23% supplemental wage withholding rate for bonuses is among the highest flat rates in the country. Here is how it compares to the states where California workers are most likely to have cross-border questions.

The practical takeaway: a $50,000 bonus paid in California results in approximately $5,115 in California withholding. That same bonus paid to a resident of Washington, Nevada, or Florida results in zero state withholding — a difference of over $5,000 in upfront cash flow and potential total tax liability.

Common Mistakes to Avoid

• Treating 10.23% as your final tax rate. The withholding rate is a collection mechanism, not a tax determination. A low-income year may mean your true California rate is 6% or 7%, and you will receive a refund. A high-income year could mean your true rate is 12.3% or 13.3%, and you will owe the difference. Check your likely bracket before the bonus arrives.
• Assuming all supplemental wages use the same rate. Telling a colleague "the California bonus tax is 10.23%" is only correct for bonuses and stock options. Commissions, overtime, and severance are withheld at 6.6%. Misclassifying the payment type causes employers to under- or over-withhold.
• Ignoring estimated payments after a large equity event. If you receive a significant RSU vesting and your income will exceed $500,000, the 10.23% withholding covers less than your actual California liability. Not making quarterly estimated payments can trigger underpayment penalties even if you pay in full when you file.
• Nonresidents not filing to claim a refund. Many California employers withhold California tax on bonuses paid to out-of-state employees who performed all their work outside California. Those employees often leave the money on the table because they do not realize they should file a California nonresident return (Form 540NR) to get it back.
• Assuming a post-move vesting event is free of California tax. Moving to Texas or Nevada before your RSUs vest does not automatically eliminate California's claim. The FTB's grant-to-vest apportionment method allocates a portion of the gain to California based on the time you spent as a California employee during the vesting period.
• Not verifying the aggregate method impact. If your bonus appears on your regular paycheck, ask payroll explicitly which method they used. The difference between the percentage and aggregate methods can be hundreds or thousands of dollars in a single paycheck — money you will eventually recover but cannot use in the meantime.

Frequently Asked Questions

• What is California's bonus tax rate?

  California's bonus withholding rate is 10.23% for bonuses and stock options. This is a flat rate applied to the gross bonus at the time of payment, separate from the employee's regular income tax bracket. Your actual California tax liability may be higher or lower depending on your total annual income.

• How do I calculate the 10.23% California bonus tax?

  Multiply your gross bonus by 0.1023. A $5,000 bonus: $5,000 × 0.1023 = $511.50 in California withholding. Add federal (22%), Social Security (6.2%), Medicare (1.45%), and the current SDI rate to find your total withholding.

• What is the difference between the 10.23% and 6.6% California supplemental rates?

  The 10.23% rate applies specifically to bonuses and stock options (NQSOs, RSUs). The 6.6% rate applies to all other supplemental wages: commissions, overtime pay, severance, vacation pay, sales awards, and back pay. The distinction is based on the nature of the payment, not the amount.

• Why was my bonus taxed at 40% in California?

  The 40% you saw is the combined effect of four separate taxes: federal income tax (22%) + California state income tax (10.23%) + Social Security (6.2%) + Medicare (1.45%) = approximately 39.88%. This is withholding, not your permanent tax rate. If your effective income tax rate is lower than the flat withholding rates, you will receive a refund.

• Do I pay California tax on a bonus if I live in another state?

  It depends on where you performed the work. If you are a nonresident and the bonus compensates you for services performed in California, the bonus is California-source income and California withholding applies. If all your work was performed outside California, the bonus is generally not taxable by California — and if your employer withheld California tax anyway, you can claim a refund by filing Form 540NR.

• Are stock options and RSUs taxed at the 10.23% rate in California?

  Yes, at the withholding level. NQSOs and RSUs are subject to 10.23% California withholding at exercise or vesting. However, if your total income places you in California's 12.3% or 13.3% top brackets, you will owe additional California tax at filing. ISOs have special rules and may trigger AMT — consult a tax professional.

• What is the aggregate method for California bonus tax?

  The aggregate method adds the bonus to your regular wages for the same pay period and applies the standard California withholding tables to the combined total. Because the combined amount falls into a higher withholding bracket, you typically have more California tax withheld than the flat 10.23% method would produce. Any extra withholding is credited toward your annual tax liability.

• When did the 10.23% California bonus tax rate take effect?

  The 10.23% flat withholding rate for bonuses and stock options was established by the California EDD and took effect on November 1, 2009. While the rate has remained at 10.23% since then, supplemental wage rates are subject to change. Always verify the current rate at edd.ca.gov.

• Can I adjust my withholding to reduce California bonus tax?

  No. The 10.23% flat withholding rate on bonuses is fixed — your DE 4 allowances and regular withholding elections do not affect it. Similarly, adjusting your federal W-4 does not change the 22% federal supplemental rate applied to bonuses. What you can do is make sure you are not over-withholding on your regular paychecks to compensate, and make estimated payments if you expect to under-withhold overall.

• What is the total tax on a $10,000 bonus in California?

  A $10,000 bonus typically results in approximately $2,200 federal withholding (22%), $1,023 California withholding (10.23%), $620 Social Security (6.2%), and $145 Medicare (1.45%), for a combined total of roughly $3,988 before SDI. Add the current SDI rate for the full figure. Approximately $6,000–$6,100 typically reaches your bank account. Your actual year-end tax liability may be higher or lower depending on your total income.

• Can I move to another state before my bonus is paid to avoid California tax?

  Only if the bonus compensates you for services performed after you established residency in the new state and outside California. If the bonus relates to work performed while you were a California resident or employee, California taxes the income regardless of where you live when you receive the payment. For RSUs, the grant-to-vest apportionment method gives California a proportional claim. Timing strategies require careful planning with a tax professional who specializes in California multistate taxation.

Tools & Resources

• EDD Publication DE 231PS — Information Sheet on Supplemental Wage Payments
  edd.ca.gov/pdf_pub_ctr/de231ps.pdf
• EDD DE 44 California Withholding Schedules — Employer withholding tables (confirm you are using the current year's edition; the EDD publishes updated schedules annually)
  edd.ca.gov (search "DE 44" for the current year)
• California FTB — Forms and Publications — Form 540, 540NR, and estimated payment vouchers
  ftb.ca.gov
• DE 4 Form — California Employee's Withholding Allowance Certificate
  edd.ca.gov/pdf_pub_ctr/de4.pdf
• FTB Form 5805 — Underpayment of Estimated Tax by Individuals and Fiduciaries
  ftb.ca.gov/forms (search "5805" for the current year's version)
• IRS Publication 15 (Circular E) — Employer's Tax Guide — federal supplemental wage withholding rules
  irs.gov/pub/irs-pdf/p15.pdf

Glossary of Terms

Supplemental Wages

Compensation paid in addition to an employee's regular wages. Includes bonuses, commissions, overtime pay, severance, vacation pay, and stock options. Different California withholding rates apply depending on the type.

PIT (Personal Income Tax)

California's state income tax, administered by the Franchise Tax Board. The 10.23% bonus withholding is a prepayment toward the employee's annual PIT liability.

EDD (Employment Development Department)

The California state agency that administers employer payroll tax withholding, including the supplemental wage rates and withholding schedules.

FTB (Franchise Tax Board)

The California state agency that administers and collects personal income tax. Employees file their annual California tax returns with the FTB.

DE 4

California Employee's Withholding Allowance Certificate. The state equivalent of the federal W-4, used to determine regular-pay withholding. It does not affect the flat supplemental wage rates.

W-4

Federal Employee's Withholding Allowance Certificate. Determines federal income tax withholding on regular wages. The flat 22% supplemental rate applies to bonuses regardless of W-4 elections.

SDI (State Disability Insurance)

California's employee-paid disability insurance program. Since 2024, the SDI rate applies to all wages with no annual wage cap. The rate is set by the EDD each year.

OASDI (Old-Age, Survivors, and Disability Insurance)

The formal name for Social Security. Withheld at 6.2% on wages up to the annual wage base, which is adjusted each year by the Social Security Administration.

Aggregate Method

A withholding calculation approach that combines supplemental wages with regular wages in the same pay period and applies the standard withholding tables to the total. Often produces higher withholding than the flat percentage method.

Grant-to-Vest Apportionment

California's method for taxing equity compensation (RSUs, stock options) when an employee has worked both inside and outside California during the vesting period. California taxes only the portion of the gain attributable to time spent as a California employee.