Everything you need to know about Form 540

What is Form 540?

Form 540 is the California Resident Income Tax Return — the primary state income tax filing for full-year California residents. It's submitted annually to the California Franchise Tax Board (FTB) and reports income, deductions, credits, and tax liability for the calendar year. Nonresidents and part-year residents use Form 540NR instead, while some taxpayers can use the simplified Form 540 2EZ.

Who should file Form 540?

You file Form 540 if you were a California resident for the full tax year and your gross income meets the state's filing threshold for your filing status and age. Most full-year California residents who earned wages, self-employment income, retirement income, capital gains, or rental income within the year will need to file — even if no California tax is owed.

What you'll need to complete it?

Have your federal Form 1040 ready since Form 540 starts from federal adjusted gross income. You'll also need W-2s and 1099s, documentation for California-specific additions and subtractions (state tax refund, U.S. government interest, HSA contributions, depreciation differences), and records for any credits you claim — the California Earned Income Tax Credit (CalEITC), Young Child Tax Credit, Dependent Exemption Credit, Child and Dependent Care Expenses Credit, Renter's Credit, and others.

When and how to file?

Form 540 is due April 15, or the next business day if April 15 falls on a weekend or holiday. California grants an automatic six-month extension to file — no form required — but any tax owed is still due by April 15 (use Form FTB 3519 to pay with the extension). E-file through CalFile, an approved tax preparer, or mail the completed return to the Franchise Tax Board address printed in the Form 540 booklet. Keep a signed copy and all supporting schedules for your records.