If you earn 1099 or self-employment income in California, the IRS and the state both expect you to pay taxes as you go, in four quarterly installments rather than one April bill. This calculator estimates your 2026 quarterly payments across all three pieces: federal self-employment tax, federal income tax, and California state income tax. California front-loads estimated taxes: 30% is due in Q1, 40% in Q2, nothing in Q3, and 30% in Q4, not four equal payments. Enter your expected net self-employment income, any W-2 wages, and your filing status to see what to send each quarter, your due dates, and how the safe-harbor rules protect you from an underpayment penalty. Everything is an estimate for planning. Always confirm with the California Franchise Tax Board before you file.
Self-employment income has no tax withheld for you, so both the IRS and California Franchise Tax Board ask you to prepay in quarterly installments. On the federal side you owe self-employment tax (15.3% Social Security and Medicare on 92.35% of your net profit, up to the Social Security wage base) plus federal income tax on your profit after the standard deduction. On top of that, California applies its own income tax.
California generally requires estimated payments once you expect to owe more than $500 in state tax for the year. California front-loads its estimated payments and uses a non-standard schedule: 30% is due by April 15, 40% by June 15, 0% in September, and the final 30% by January 15. There is no third-quarter payment. Unlike the federal system's equal quarters, California weights its installments (30% / 40% / 0% / 30%), so the amount due changes from quarter to quarter.
You avoid an IRS underpayment penalty by hitting a "safe harbor": paying at least 90% of this year's total tax, or 100% of last year's (110% if your income is higher). California applies a nine-bracket graduated tax (1% to 12.3%) to your federal AGI after the California standard deduction ($5,706 single / $11,412 married), plus an extra 1% Mental Health Services Tax on taxable income over $1 million (a 13.3% top marginal rate). California grants personal exemptions as tax credits rather than deductions; those credits are not yet modeled here, so this estimate can run slightly high. Estimated payments follow California's own 30/40/0/30 quarterly weighting, not equal quarters. You can pay online through the California Franchise Tax Board portal, and the calculator above breaks your total into the federal and California pieces so you can send each to the right place. You can pay online at the California Franchise Tax Board (payment portal).
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For educational purposes only, not tax advice. Tax rules change and individual situations vary; confirm figures with a tax professional and the California Franchise Tax Board before filing. State tax data last verified pending.
Sources: ftb.ca.gov, ftb.ca.gov.