What Form 540 Is and Who Files It

California has three personal income tax returns: the 540 (full-year residents), the 540NR (part-year and nonresidents), and the 540 2EZ (simplified version with income limits). Most people living and working in California file the standard 540.

You’re a full-year resident if California was your domicile for the entire tax year — or if you were physically present in the state for more than nine months, even if you didn’t consider it “home.” California’s definition of residency is broader than most states, and the Franchise Tax Board doesn’t shy away from asserting it. If you split time between California and another state, that’s a 540NR situation, not a 540.

The 540 doesn’t exist in a vacuum. It’s built on top of your federal return. Your federal adjusted gross income (AGI) flows directly onto line 13, and from there California makes its own modifications. So you can’t file your 540 until your federal 1040 is done — or at least drafted far enough to have a final AGI number.

One thing worth knowing up front: California does not conform to every federal tax provision. Some deductions the IRS allows, the FTB doesn’t. Some income the IRS excludes, California taxes. That’s what Schedule CA (540) is for, and we’ll get into it below.

Filing Status and Exemptions (Lines 1–10)

Lines 1 through 5 on Form 540 ask for your filing status. California recognizes the same five statuses as the IRS — single, married filing jointly, married filing separately, head of household, and qualifying surviving spouse. Your California filing status almost always matches your federal one, but there’s a wrinkle for registered domestic partners: California treats them as married for state tax purposes, even though federal status might differ.

Lines 7 through 10 handle exemptions. California still uses a personal exemption system. For 2024, each personal exemption credit is worth roughly $144 (it adjusts for inflation each year). You get one for yourself, one for your spouse if filing jointly, and one for each dependent. There are additional exemption credits if you or your spouse are 65 or older, or legally blind.

This is different from the federal return. The Tax Cuts and Jobs Act zeroed out federal personal exemptions through 2025, but California never followed suit. You’ll still claim these exemptions on your 540, and they’ll reduce your tax — just not by very much. The real savings come from credits and deductions further down the form.

Income (Lines 11–16)

Here’s where your federal return and your California return start talking to each other. Line 13 asks for your federal AGI — the number from line 11 of your federal 1040. You copy it over directly. California doesn’t recalculate your gross income from scratch; it takes the federal number and then adjusts.

Lines 14 and 15 are where Schedule CA (540) enters the picture. Line 14 picks up California additions to income — things the federal return excluded that California wants to tax. Line 15 picks up subtractions — income that California excludes even though the feds taxed it. Line 16 is your California adjusted gross income: federal AGI plus additions, minus subtractions.

If your income is entirely from a W-2 job in California with no unusual items, lines 14 and 15 might both be zero. But if you have out-of-state bond interest, HSA contributions, Social Security income, or stock option differences, you’ll have numbers on those lines. More on that in the next section.

California Adjustments — Schedule CA (540)

Schedule CA is the bridge between your federal return and your California return. It’s where you identify every place California’s tax law differs from the IRC, and it’s one of the more tedious parts of a California return because there are a lot of differences.

Common Additions (Income California Taxes That the Feds Don’t)

Out-of-state municipal bond interest. If you hold muni bonds from New York, Texas, or any state other than California, the interest is tax-free on your federal return but taxable on your California return. Only bonds issued by California or its municipalities get the state exemption. We see this catch people off guard every year — especially clients who moved from the East Coast and kept their old bond portfolio.

HSA contributions. California doesn’t recognize Health Savings Accounts. Contributions you deducted on your federal return get added back on Schedule CA. The HSA earnings are taxable too. This is one of those areas where California flat-out refused to conform, and it creates extra recordkeeping if you have an HSA.

Stock option timing differences. California’s sourcing rules for stock options and RSUs don’t always match federal treatment, especially if you earned the equity in one state and exercised it in another. The allocation formulas on Schedule CA can get complicated quickly.

For a full walkthrough of every addition and how to handle each one, see our Schedule CA additions guide.

Common Subtractions (Income California Exempts That the Feds Tax)

Social Security benefits. California doesn’t tax Social Security income. Period. If you reported Social Security on your federal return, you subtract the full amount on Schedule CA. This is one of the few genuinely taxpayer-friendly California rules.

Military pay for active-duty service. Pay earned by active-duty military members while stationed outside California is subtracted on Schedule CA.

California lottery winnings. Winnings from the California State Lottery are exempt from state income tax (though not from federal). If you had lottery winnings included in your federal AGI, subtract them here.

The full list of additions and subtractions runs several pages. Schedule CA mirrors the federal 1040 line by line, so every line on the 1040 has a corresponding adjustment opportunity on the CA. Our Schedule CA subtractions guide covers each one in detail.

Deductions (Lines 17–19)

After California AGI, you take either the standard deduction or itemized deductions. California’s standard deduction for 2024 is $5,540 for single filers and $11,080 for married filing jointly. That’s well below the federal amounts ($14,600 and $29,200), which is why more California filers end up itemizing at the state level than at the federal level.

If you itemize, you’ll use the California version of Schedule CA (Part II) to compute your California itemized deductions. California doesn’t conform to all federal itemized deduction rules. The biggest difference: California caps the state and local tax (SALT) deduction on the federal return at $10,000, but that cap doesn’t apply on the California return in the same way — because you’re not deducting California income tax against itself. You are, however, deducting things like mortgage interest, charitable contributions, and casualty losses, with some California-specific modifications.

There’s no separate “qualified business income deduction” on California’s return either. The federal Section 199A deduction doesn’t exist for California purposes, which means pass-through business owners get a larger taxable income number on their 540 than on their 1040.

Tax Calculation (Lines 31–35)

California’s income tax rates are progressive and steep. The brackets range from 1% on the first few thousand dollars of taxable income up to 12.3% on income over about $700,000 (for single filers). And then there’s the extra 1% mental health services tax — officially the Mental Health Services Tax — on taxable income exceeding $1,000,000. That brings the top marginal rate to 13.3%, the highest state income tax rate in the country.

Unlike the federal system, California does not give preferential treatment to long-term capital gains. Gains that get taxed at 15% or 20% on your federal return are taxed at your ordinary rate in California. For high-income clients — especially those in Los Angeles with significant investment income — this is the single biggest California tax hit. A $500,000 long-term capital gain that’s taxed at 20% federally is taxed at 13.3% in California. There’s no discount.

Line 31 is where you look up your tax using the tax table or the tax rate schedule. Line 35 captures the mental health services tax if applicable. There’s also a use tax line on the 540 — California’s way of collecting sales tax on out-of-state purchases where the seller didn’t charge California tax. Most people either use the lookup table estimate or report actual purchases.

Credits (Lines 40–48)

Credits reduce your tax dollar for dollar, which makes them more valuable than deductions. California offers several that don’t exist at the federal level.

California Earned Income Tax Credit (CalEITC). This is California’s own earned income credit, available to filers with earned income under about $30,000–$31,000 (the threshold adjusts annually). It stacks on top of the federal EITC, so qualifying taxpayers get both.

Young Child Tax Credit (YCTC). If you qualify for CalEITC and have a child under age 6, you get an additional credit. For 2024 returns, this is worth up to roughly $1,117.

Renter’s credit. A small nonrefundable credit for California residents who rent their primary home and meet income limits. It’s $60 for single filers and $120 for joint filers. Not life-changing money, but it’s free and a lot of people forget to claim it.

PTE elective tax credit (Form 3804-CR). If you’re a partner or S-corp shareholder whose entity made the California pass-through entity tax election, you claim your share of the PTE tax paid as a credit on line 43. This is one of the workarounds California created after the SALT cap, and it’s worth real money for owners of profitable pass-through businesses. The entity pays the tax, and you get a credit on your personal return — effectively bypassing the $10,000 SALT limitation on the federal side.

Other credits. California has credits for child and dependent care, excess SDI, taxes paid to other states (the OSTC), which prevents double taxation if you earned income in another state, and a long list of more specialized credits. Lines 40 through 48 capture all of them. Your total credits offset your tax from the earlier lines.

Other Taxes (Lines 61–64)

Most filers don’t owe anything in this section, but it’s not empty for everyone. Line 61 picks up the mental health services tax (if it wasn’t already captured in the tax computation). Line 63 covers excess SDI or VPDI withholding — if you had multiple employers during the year and each one withheld State Disability Insurance, you may have overpaid. That overpayment shows up here and gets refunded.

There’s also a penalty line for early distribution from retirement accounts if California’s treatment differs from federal, and an “other taxes” catch-all for things like the tax on accumulation distributions from trusts or the recapture of certain credits.

Payments and Refund (Lines 71–115)

The bottom of the 540 is where you reconcile what you owe with what you’ve already paid. Line 71 reports California income tax withheld from your W-2s and 1099s. Line 72 picks up estimated tax payments — those quarterly payments due April 15, June 15, September 15, and January 15. Line 73 captures any amount you paid with an extension (Form 3519).

If your total payments exceed your total tax, you get a refund. You can have it direct-deposited (California supports splitting between up to two bank accounts) or receive a paper check. If your total tax exceeds your payments, you owe the difference — and if you didn’t make adequate estimated payments throughout the year, you’ll likely owe a penalty too. California’s underpayment penalty is calculated on Form 5805.

One thing to watch: California’s refund can take noticeably longer than the federal refund. The FTB processes returns on a different timeline than the IRS, and if your return triggers a manual review, the wait can stretch to several months.

California Quirks Worth Knowing

No capital gains preference. We mentioned this above, but it’s worth repeating because it’s the single most expensive difference between California and the federal system for high-income taxpayers. Long-term capital gains are taxed as ordinary income. Full stop. For more on this, see our California capital gains tax guide.

Community property rules. California is a community property state. If you’re married filing separately, you generally split community income 50/50 between spouses — regardless of who actually earned it. This applies to wages, business income, and investment income from community assets. It makes MFS returns in California more complicated than in common-law states, and it catches people off guard during divorce proceedings.

The PTE election. The pass-through entity elective tax is now a permanent fixture of California’s tax code (AB 150). It’s the closest thing to a legal workaround for the $10,000 federal SALT cap. If you own a share of an S-corp or partnership doing business in California, this election should be on your radar every year.

Residency audits. California is one of the most aggressive states when it comes to residency audits. If you leave California and claim nonresident status, the FTB will look at your phone records, credit card statements, medical providers, and social media posts. The burden of proof is on you to show you left. This matters for the 540 because filing a 540 (resident return) is straightforward — it’s when you stop filing one that the FTB starts asking questions.

If you’re comparing California’s approach with another major state, our NY IT-201 line-by-line guide walks through New York’s equivalent form.

Sources & References

• California Form 540 Instructions and Tax Booklet (ftb.ca.gov)
• Schedule CA (540) Instructions — California Adjustments (ftb.ca.gov)
• California Standard and Itemized Deductions (ftb.ca.gov)
• California Earned Income Tax Credit (CalEITC) (ftb.ca.gov)
• Young Child Tax Credit (ftb.ca.gov)
• Mental Health Services Tax (ftb.ca.gov)
• California Residency Status and Domicile (ftb.ca.gov)
• California Estimated Tax Payments (ftb.ca.gov)
• IRS Form 1040 — U.S. Individual Income Tax Return (irs.gov)
• IRS Topic 551 — Standard Deduction (irs.gov)
• 26 U.S.C. §1 — Tax Imposed, Including Capital Gains Rates (law.cornell.edu)
• 26 U.S.C. §164 — Taxes / SALT Deduction (law.cornell.edu)
• 26 U.S.C. §199A — Qualified Business Income Deduction (law.cornell.edu)