How to Do Taxes in California: Forms, Deadlines, and Credits

To file California state taxes, complete your federal return first, then file Form 540 (or the simpler Form 540 2EZ if you qualify) with the Franchise Tax Board by April 15, 2026. Most residents can file free through CalFile, the FTB’s own online system, or submit through commercial tax software that handles both returns together. California builds directly on your federal numbers, so the state return is mostly a matter of carrying figures over and making a handful of California-specific adjustments.

Do You Have to File

Your filing obligation depends on residency and income. California treats you as a resident if you’re in the state for anything beyond a short-term or passing reason, even without a formal declaration of residency.¹

For the 2025 tax year, you generally must file if your gross income exceeds:

$22,941 for a single filer under 65 with no dependents (or $18,353 in adjusted gross income)
$45,887 for a married couple filing jointly, both under 65, no dependents ($36,711 AGI)
$30,591 for a single filer 65 or older with no dependents ($26,003 AGI)

Thresholds go up with dependents. A single filer under 65 with one dependent doesn’t have to file until gross income tops $38,774.² File anyway if you had California tax withheld and want a refund, or if you qualify for refundable credits like CalEITC.

Pick the Right Form

Three forms cover most situations:

Form 540 2EZ. For full-year residents with simple returns. Your income has to come only from wages, taxable interest, dividends, pensions, unemployment, or Social Security, and you can claim only the standard deduction with no adjustments to income.³
Form 540. The standard resident return. Use it for itemized deductions, adjustments like student loan interest, self-employment income, or anything the 2EZ doesn’t cover.²
Form 540NR. For nonresidents and part-year residents with California-source income.

Not sure whether you can use the 2EZ? Start there. The FTB’s qualification checklist walks through every restriction, and if you don’t qualify, it steers you to the full 540.

What to Have Ready Before You Start

Finish your federal Form 1040 first. Your federal adjusted gross income from line 11 flows into line 13 of the California Form 540, and most state calculations start from that figure.² You then use Schedule CA (540) to make California-specific adjustments, since the state doesn’t conform to every federal rule.⁴

Pull these together first:

W-2s from every employer
1099 forms for interest, dividends, freelance and gig work, retirement distributions, and 1099-Ks from payment apps if you had reportable transactions
Social Security numbers or ITINs for you, your spouse, and each dependent
Last year’s return, which helps with carryovers and prior-year AGI verification for e-filing

Some income taxed federally is exempt in California, and vice versa. U.S. Treasury bond interest is exempt on your California return. Interest from another state’s municipal bonds is federally tax-free but taxable in California. Schedule CA is where those differences get sorted out.

How to Submit Your Return

You have three ways to file.

CalFile is the FTB’s free e-filing tool for full-year residents who meet the qualifications, including claiming 10 or fewer dependents.⁵ It handles only your state return, so you still need a separate route for the federal side. You get real-time confirmation and the fastest refund processing available.⁶

Commercial tax software bundles federal and state into one session. Most products charge for the state return, typically $25 to $60 depending on the tier. This is where filers with itemized deductions or self-employment income usually end up.

Paper filing works but takes longest. Sign in ink, keep the main form on top with schedules behind it, and mail to the right address. Returns with no payment go to Franchise Tax Board, PO Box 942840, Sacramento, CA 94240-0001. Returns with payment go to PO Box 942867, Sacramento, CA 94267-0001.⁷

Deadlines and the Extension Trap

Your 2025 California return and any tax owed are due April 15, 2026. California automatically extends the filing deadline to October 15, 2026 with no paperwork required.⁸ The trap: that automatic extension covers the return only, not the payment. Anything you owe is still due April 15, and paying in October means penalties and interest running from the original date.

If you expect to owe but need more time to file, estimate the amount and pay by April 15 using Web Pay or by mailing Form FTB 3519 with a check.⁹ A reasonable estimate protects you from most penalties even if the final return arrives later.

Credits Worth Checking For

California Earned Income Tax Credit (CalEITC) is a refundable credit for workers earning $32,900 or less, so you can receive it even if you owe no tax. The 2025 maximum is $3,756, depending on income and qualifying children.¹⁰ You need a valid SSN or ITIN for yourself and each qualifying child. Self-employment income counts toward the earned income requirement.

Young Child Tax Credit (YCTC) is available if you qualify for CalEITC and have a child under six at year-end. The 2025 credit is worth up to $1,189 per eligible return, with the same $32,900 income limit.¹¹

Nonrefundable renter’s credit applies if you rented your home for at least half the year and your California income is below $53,994 (single) or $107,987 (married filing jointly). The credit is $60 for single filers and $120 for joint filers or heads of household.¹² Small money, but it takes seconds to claim. You can’t claim it if you lived in tax-exempt housing or someone else claims you as a dependent.

Paying What You Owe

The FTB accepts several payment methods:

Web Pay. Free direct transfer from your bank account through the FTB portal. Fastest and cheapest.
Credit or debit card. Available through third-party processors with a 2.3% service fee. On a $5,000 bill, that adds $115.¹³
Check or money order. Mail with Form FTB 3519 to PO Box 942867, Sacramento, CA 94267-0008. Write your Social Security number and “2025 FTB” on the check so it’s credited correctly.⁹

If You File or Pay Late

California charges separate penalties for filing late and paying late, and they can stack.

The failure-to-file penalty is 5% of unpaid tax for each month or partial month the return is late, up to 25%.¹⁴ The clock runs from April 15, not the extended October date. On a $4,000 balance filed five months late without an extension payment, the penalty alone reaches $1,000.

The failure-to-pay penalty is a separate 5% of unpaid tax, plus 0.5% for each month the balance remains outstanding, up to 40 months. It also caps at 25% of unpaid tax.¹⁵

Interest also runs on any unpaid balance. The current rate is 7% per year, compounded daily, through June 30, 2026.¹⁶ The same 7% applies to estimated tax underpayment penalties. Interest accrues from the original due date until you pay in full, whether or not you’ve filed.

Quarterly Payments If You Have Untaxed Income

If you earn income without California withholding, such as freelance work, rental income, or investment gains, you likely need to make quarterly estimated payments. California’s schedule is uneven and different from the federal one:

April 15, 2026: 30% of estimated annual tax
June 15, 2026: 40% of estimated annual tax
September 15, 2026: no payment due (unlike federal)
January 15, 2027: 30% of estimated annual tax

Use Form 540-ES to calculate and submit these payments.¹⁷ The 30/40/0/30 split catches people off guard, because the federal schedule is four equal 25% installments. If you’re used to the federal rhythm, don’t assume it carries over.

1
CA.gov. Residents
2
CA.gov. 2025 Personal Income Tax Booklet – California Forms and Instructions 540
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CA.gov. 2025 Form 540 2EZ – Personal Income Tax Booklet
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CA.gov. 2025 Instructions for Schedule CA (540)
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CA.gov. CalFile Qualifications 2025
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CA.gov. CalFile
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CA.gov. Mailing Addresses
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CA.gov. Due Dates Personal
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CA.gov. Extension to File
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CA.gov. California Earned Income Tax Credit
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CA.gov. Young Child Tax Credit
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CA.gov. Nonrefundable Renter’s Credit
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CA.gov. Pay by Credit Card
14
Justia. California Revenue and Taxation Code Article 7 – Penalties and Additions to Tax
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CA.gov. FTB 1024 – Penalty Reference Chart
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CA.gov. Interest and Estimate Penalty Rates
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CA.gov. 2026 Instructions for Form 540-ES Estimated Tax for Individuals