California Estimated Taxes Guide

Who Must Pay Estimated Taxes

Estimated taxes are quarterly prepayments of income tax for taxpayers whose income is not subject to withholding — primarily self-employed individuals, business owners, freelancers, and investors with significant capital gains or dividend income. If you expect to owe at least $1,000 in federal income tax after subtracting withholding and credits, you are generally required to make estimated tax payments. California has a similar $500 threshold for state estimated taxes.

Federal Estimated Tax Rules

Federal estimated taxes are paid quarterly using Form 1040-ES. The IRS requires quarterly payments — not monthly or annual. Missing a quarterly payment triggers an underpayment penalty even if you pay the full amount owed when you file your return. The penalty is calculated separately for each quarter, so a large Q4 payment does not cure an underpayment in Q1.

California Estimated Tax Rules

California estimated taxes are paid using FTB Form 540-ES. California's estimated tax schedule is different from the federal schedule — California requires larger payments in Q1 and Q2 and smaller payments in Q3 and Q4. This front-loaded schedule catches many taxpayers off guard. KDA calculates California estimated taxes separately from federal estimated taxes for every self-employed client.

2026 Due Dates

Note: California requires 30% of annual estimated tax in Q1, 40% in Q2, 0% in Q3, and 30% in Q4. The federal schedule is 25% per quarter. This difference is a common source of California underpayment penalties.

Safe Harbor Rules

You can avoid underpayment penalties by meeting one of the safe harbor rules: (1) Pay 100% of the prior year's tax liability (110% if your prior year AGI exceeded $150,000 for federal; 110% for California regardless of income). (2) Pay 90% of the current year's tax liability. The prior-year safe harbor is generally the safer choice for taxpayers with variable income — it gives you a fixed target regardless of how your current year income develops.

Underpayment Penalties

The federal underpayment penalty is the federal short-term rate plus 3% — currently approximately 7–8% annually, calculated on the underpaid amount for each quarter. California's underpayment penalty rate is similar. The penalty is not a flat fee — it is interest-like, calculated on the shortfall for each day it exists. KDA calculates estimated tax payments for every self-employed client to minimize underpayment penalties while avoiding overpayment.