This guide is for California residents, people who moved during the year, nonresidents with California-source income, and remote workers. It covers choosing the right forms, preparing both returns, meeting deadlines, finding official resources, and avoiding common mistakes. Figures refer to tax year 2025 returns unless noted.
Key Takeaways
- Form 1040 goes to the IRS; California returns go to the FTB.
- Residency and income source decide between Form 540, 540NR, or 540 2EZ.
- Finish the federal return first, then review California adjustments.
- An extension to file is not an extension to pay.
- Use current-year IRS and FTB forms, not outdated copies.
California Form 1040 Explained: Federal Form 1040 vs. California Returns
The IRS describes Form 1040 as the annual income tax return used by U.S. taxpayers. It reports income, adjustments, deductions, credits, payments, and the resulting refund or balance due.
California's individual returns are the 540 family: Form 540, Form 540NR, and Form 540 2EZ. Form 540 2EZ remains available for tax year 2025 for eligible full-year residents.
Which Agency Handles What
| Item | IRS (federal) | FTB (California) |
|---|---|---|
| Return | Form 1040 | Form 540, 540NR, or 540 2EZ |
| Payments | IRS Direct Pay | FTB Web Pay |
| Refund status | IRS refund tools | FTB Where's My Refund |
| Return copies | IRS transcripts, Form 4506 | MyFTB, Form 3516 |
How Federal Numbers Flow to California
Form 540 line 13 starts with federal AGI from Form 1040 line 11b. Schedule CA then applies California subtractions and additions. Schedule CA (540NR) also splits California-source income from resident-period income.
Federal AGI is only a starting point. For tax year 2025, California:
- Does not tax Social Security benefits
- Does not allow the federal HSA contribution deduction
- Does not conform to the federal foreign earned income and housing exclusions
- Uses its own standard deduction: $5,706 for single filers and $11,412 for joint filers, heads of household, and qualifying surviving spouses
Federal and California taxable income often differ.
Who Must File and Which California Return Should You Use?
Residency drives the answer. FTB's Publication 1031 explains the analysis in detail.
- Resident: in California for other than a temporary or transitory purpose, or domiciled in California while away temporarily
- Part-year resident: a resident for part of the year, a nonresident for the rest
- Nonresident: anyone who is not a resident
Domicile is your true, fixed, permanent home. Being present in a state and being domiciled there are separate questions.
Form Selection at a Glance
| Status | Income California taxes | Return |
|---|---|---|
| Full-year resident | All sources | 540, or 540 2EZ if eligible |
| Part-year resident | Worldwide while resident; California-source while nonresident | 540NR |
| Nonresident | California-source only | 540NR |
Form 540 2EZ is limited. It requires full-year residency, limited income types, no adjustments, and the standard deduction. Income caps are $100,000 for single and head of household filers and $200,000 for joint filers.
Tax Year 2025 Filing Thresholds
You generally must file when California gross income or California AGI exceeds the chart amount for your status. Here are two sample rows (0 dependents):
| Status | Gross income | AGI |
|---|---|---|
| Single, under 65 | $22,941 | $18,353 |
| Married/RDP, both under 65 | $45,887 | $36,711 |
The 2025 Form 540 instructions list thresholds for every age and dependent combination. Special filing rules can apply below these amounts. Filing may also be worthwhile to recover withheld tax even when you are under the threshold.
Remote Workers and California-Source Income
California-source income includes wages for work performed in California, California rental income, and income from a California business. A nonresident employee who moves away and works entirely outside California does not have California-source wages just because the employer is there. Independent contractors are different: FTB looks at where the customer receives the benefit.
Situations That Need Extra Care
- Capital gains: Schedule D (540) when California and federal amounts differ
- Passive losses: Form 3801
- Dependent care credit: Form 3506
- Other-state tax credit: Schedule S (not for foreign taxes)
- Contractors reclassified under California law: an adjustment to the self-employment tax deduction
- Foreign income: a possible California addition
Before choosing a return, write down your move dates, work locations, California-source income, and withholding. Those facts decide everything else.
How to Prepare and File Your Federal and California Returns
Gather Your Documents
- Taxpayer and dependent identification
- W-2s and 1099s, including 1099-R
- Form 1095-A if you had Marketplace coverage
- Prior federal and state returns
- Bank routing and account numbers
- Childcare provider details
- Estimated payment and withholding records
- Business, rental, and brokerage records where they apply
Prepare Form 1040 First
- Report all income and select your filing status.
- Claim adjustments, then the standard or itemized deduction.
- Complete required schedules and review dependents.
- Calculate tax, payments, and your refund or balance due.
Then Build the California Return
Carry over federal AGI, then work through Schedule CA. Review California wages, deductions, credits, and any income the state treats differently from federal rules. Do not copy federal taxable income across.
Choose How to File
Federal returns can be e-filed or mailed. Paper returns must be signed, and both spouses sign a joint return. California requires e-file authorization before transmission.
| Option | Notes |
|---|---|
| IRS Free File guided software | 2026 season (tax year 2025): AGI of $89,000 or less |
| IRS Free File Fillable Forms | No income limit |
| FTB CalFile | Free direct e-file for eligible taxpayers; supports tax year 2025 |
| IRS Direct File | Not available for the 2026 filing season |
Program availability changes by season, so confirm eligibility on the IRS and FTB sites. IRS Direct Pay and FTB Web Pay take bank payments with no service fee.
Form 540 lets you split a refund between two accounts. For paper filing, use the IRS "where to file" directory and the mailing instructions in the FTB booklet.
Final Review Checklist
- Names and taxpayer ID numbers
- Filing status and residency status
- Federal and state income figures
- Withholding and estimated payments
- Bank details
- Schedules and attachments
- Payment confirmation and e-file acceptance records
Deadlines, Extensions, Payments, and Recordkeeping
For tax year 2025, the federal and California filing and payment deadline was April 15, 2026. California's automatic extension ran to October 15, 2026 with no application. Federal Form 4868 generally adds six months to file.
Neither extension moves the payment date. Estimate what you owe and pay by April 15. Weekend and holiday due dates shift to the next business day. Disaster relief is separate and applies only to eligible taxpayers, as with the Los Angeles County wildfire postponements.
Penalties for Late Filing or Payment
- IRS failure to file: 5% of unpaid tax per month, up to 25%
- IRS failure to pay: 0.5% per month, up to 25%
- FTB delinquent filing: 5% per month, up to 25%
- FTB late payment: 5% plus 0.5% per month
Exceptions and minimums apply.
Estimated Payments for Tax Year 2026
| Schedule | Apr 15 | Jun 15 | Sep 15 | Jan 15, 2027 |
|---|---|---|---|---|
| Federal 1040-ES | 25% | 25% | 25% | 25% |
| California 540-ES | 30% | 40% | 0% | 30% |
California's schedule skips September. Special methods can change what you owe.
Records and Refund Timing
- IRS retention: generally 3 years; 6 years if you omit more than 25% of gross income; 7 years for certain bad-debt and worthless-security claims
- California: generally a 4-year limitation period
- Property basis records: keep as long as they matter
- Refunds: the IRS typically takes 3 weeks for e-filed returns and 6 or more weeks for paper; the FTB takes up to 3 weeks for e-filed and 3 months for paper
Keep submitted returns, e-file confirmations, source documents, and any notices.
Official Resources, Common Errors, and When to Get Help
Resource Map
- IRS: the Form 1040 page and instructions, Get Transcript, Form 4506-T, Form 4506, Direct Pay
- FTB: Form 540 and 540NR booklets, residency guidance, Web Pay, Where's My Refund, MyFTB
An IRS transcript is a free summary, not a photocopy. A full return copy via Form 4506 costs $30 per tax year and can take up to 75 calendar days. California copies come through MyFTB, Form 3516, or a written request, at $20 per tax year with up to four weeks of processing.
Common Errors to Avoid
- Confusing Form 1040 with Form 540
- Using the wrong tax year's instructions
- Picking the wrong residency form
- Assuming federal and California calculations match
- Skipping Schedule CA adjustments
- Sending payment to the wrong agency
- Treating an IRS transcript as your California return
- Leaving a return unsigned or missing a schedule
When Professional Help Pays Off
Consider a review if you have:
- Income from more than one state, or a move during the year
- Business or rental activity
- Equity compensation or large investment transactions
- Foreign income
- Amended returns, audits, or IRS or FTB notices
The IRS suggests an enrolled agent, CPA, or attorney for complex returns. Paid preparers need a PTIN, and nonexempt preparers in California must register with CTEC.
VJM Global prepares Form 1040 and 1040-NR returns, including for nonresident aliens with U.S.-source income. The firm also handles multi-state compliance and helps assemble documents and responses when an IRS notice arrives. Its professionals are trained in U.S. accounting and regulatory practices and work remotely with U.S. taxpayers.
Frequently Asked Questions
What is Form 1040 and is it the same as a tax return?
Form 1040 is the main federal individual income tax return. "Tax return" is the broader term for any federal or state filing, so California's Form 540 is also a tax return.
Where do I file Form 1040 in California?
File it with the IRS, electronically or on paper. Your California return goes separately to the FTB. Check each agency's current instructions.
How do I get a copy of my Form 1040?
A free IRS transcript summarizes your return. For an actual copy, file Form 4506 ($30, slow processing). California copies come from the FTB separately.
Do California residents file Form 540 or Form 540NR?
Full-year residents generally file Form 540 or an eligible 540 2EZ. Part-year residents and nonresidents with California-source income use 540NR. Unusual cases need FTB guidance.
Can I owe California tax even if I do not owe federal tax?
Yes. California has its own deductions, credits, thresholds, and income rules, so a zero federal balance does not settle your state result.
