California Safe Harbor Rule for Estimated Tax Payments

California’s safe harbor rule for estimated tax payments gives you a fixed target: pay the lower of 90% of your current-year tax or 100% of last year’s tax across four installments, and the Franchise Tax Board (FTB) won’t charge an underpayment penalty even if you owe more when you file. If your prior-year California adjusted gross income (AGI) was above $150,000, the prior-year figure rises to 110%. The rule matters most if you’re self-employed, live on investment income, or otherwise earn money that isn’t run through employer withholding.

Who Has to Make Estimated Payments

California requires estimated payments only if you expect to owe at least $500 in tax for the year after subtracting withholding and credits. For married taxpayers or registered domestic partners filing separately, the threshold is $250.¹ If your withholding and credits already cover the full liability, you owe nothing more during the year no matter how much you earn.

You also need to expect that your withholding and credits will fall short of the smaller of two benchmarks: 90% of your current-year tax or 100% of last year’s tax (including any alternative minimum tax). If withholding alone covers that smaller figure, you’re clear.²

The Two Standard Safe Harbor Targets

If your prior-year California AGI was $150,000 or less ($75,000 or less if married filing separately), you qualify for the standard safe harbor. You can meet either target, whichever is lower:

90% of your current-year tax. This requires a reasonably accurate forecast of your total liability. Volatile income makes it harder.
100% of your prior-year tax. You match the total tax from last year’s Form 540, including AMT. Steady or growing income makes this the easier path because the number is already locked in.

Either one works. If last year’s tax was $12,000, paying $12,000 across the four installments fully protects you, even if your actual current-year liability turns out to be $18,000.¹

One thing catches people. If you overpaid last year and applied the refund toward this year’s estimated tax, that credit counts toward your first installment. Reduce what you send in April so you’re not double-paying.²

Higher Earners Pay 110%

If your prior-year California AGI exceeded $150,000 ($75,000 for married filing separately), the prior-year benchmark tightens from 100% to 110%.¹ You still pick whichever is lower between that 110% figure and 90% of your current-year tax.

The $1 Million AGI Cutoff

California has a rule with no federal counterpart. If your current-year California AGI reaches $1,000,000 or more ($500,000 if married filing separately), you lose access to the prior-year safe harbor completely. You must base payments on at least 90% of your current-year tax. There is no fallback to last year’s number.²

For high earners with lumpy income, this creates real risk. A $400,000 year followed by a $1,200,000 year means you can’t simply pay 110% of the prior smaller tax. You have to forecast the current year accurately enough to cover 90% of what you’ll actually owe. Underestimate, and the shortfall carries a penalty.

The 30/40/0/30 Installment Schedule

This is where California trips up people who are used to the federal system. The IRS asks for four equal 25% installments. California does not. The FTB uses an uneven schedule:¹

April 15: 30% of the required annual payment
June 15: 40% of the required annual payment
September 15: nothing is due
January 15 of the following year: 30% of the required annual payment

California doesn’t require a September payment at all, and June is the largest installment. If you set up four identical quarterly payments out of habit, you’ll be short in June and can trigger a penalty on that installment even after paying the correct annual total. If a deadline falls on a weekend or legal holiday, it shifts to the next business day.³ If you file your return by January 31 and pay the full balance then, you can skip the fourth installment without penalty.²

Annualized Income for Uneven Earnings

If your income arrives unevenly (a fourth-quarter bonus, seasonal business revenue, a one-time capital gain) the standard schedule can penalize you for not paying money you hadn’t earned yet. The annualized income installment method lets you calculate each installment based on what you actually earned through the end of that period rather than assuming income was spread evenly. Payments start small and grow with your cash flow. You still need cumulative payments by each deadline to cover the required percentage of tax on your annualized income through that date. To use this method, complete Part III of FTB Form 5805 and attach it to your return.⁴

Farmers, Fishermen, and New Residents

If at least two-thirds of your gross income comes from farming or fishing, the safe harbor drops to 66⅔% of current-year tax, and you owe a single payment by January 15 of the following year rather than following the four-installment schedule. If you file your return and pay in full by March 1 (or the next business day), you skip estimated payments altogether.²

New residents and nonresidents who had no California tax liability the prior year are exempt from estimated payments. Without a prior-year California return, the 100% or 110% prior-year method has nothing to calculate against, and the FTB doesn’t penalize the gap.²

What Happens If You Miss

Missing a safe harbor threshold isn’t a flat fine. The penalty runs like interest on whatever you should have paid but didn’t, from the installment due date until the shortfall is covered. The FTB calculates it separately for each installment, so a shortfall in April doesn’t automatically infect a June payment that was on time.

The FTB resets the estimate penalty rate every six months. For July 1, 2025 through June 30, 2026, the rate is 4%, compounded daily.⁵ Because the penalty runs on each installment independently, an April shortfall sitting unpaid until you file in October accumulates far more than a January shortfall resolved within weeks. Catching up early saves real money.

Mandatory Electronic Payment

If any single estimated tax or extension payment exceeds $20,000, or if your total tax liability on an original return exceeds $80,000, California requires you to pay electronically.⁶ Sending a paper check once you’re above these thresholds triggers a separate penalty of 1% of the amount not paid electronically.⁷ On a $25,000 payment, that’s $250 for using the wrong payment channel. The FTB accepts Web Pay, electronic funds transfer, and credit or debit card.

Form 5805 and Penalty Waivers

FTB Form 5805 is the form you use to show you met a safe harbor or to calculate what you owe if you didn’t. Attach it to the back of your Form 540 (or Form 540NR for part-year residents and nonresidents).⁸ The FTB can usually calculate the penalty for you, so filing the form yourself isn’t always required. File it if you used the annualized income method, are requesting a waiver, or want to verify the FTB’s math.

Waivers are granted narrowly. The two main grounds are:

Casualty, disaster, or other unusual circumstance where the underpayment was due to reasonable cause rather than neglect.
Retirement after age 62 or disability that arose during the tax year or the preceding year, where the underpayment was due to reasonable cause.⁹

To request a waiver, check “Yes” on Part I, Question 1 of Form 5805, write a short explanation, calculate the penalty as if no waiver existed, and note the amount you want waived on the dotted line next to the penalty total. Attach the completed form to your return.⁴ If the FTB has already assessed a penalty before you filed the form, submit it separately with a written explanation to request abatement.

1
Franchise Tax Board. Estimated Tax Payments
2
Franchise Tax Board. 2025 Instructions for Form 540-ES Estimated Tax for Individuals
3
Franchise Tax Board. Due Dates Businesses
4
Franchise Tax Board. 2024 Instructions for Form FTB 5805 Underpayment of Estimated Tax by Individuals and Fiduciaries
5
Franchise Tax Board. Interest and Estimate Penalty Rates
6
Franchise Tax Board. Mandatory e-Pay for Individuals
7
Franchise Tax Board. Common Penalties and Fees
8
Franchise Tax Board. 2024 Form 5805 Underpayment of Estimated Tax by Individuals and Fiduciaries
9
Franchise Tax Board. Instructions for Form FTB 5805 Underpayment of Estimated Tax by Individuals and Fiduciaries