California FTB Notice Request for Tax Return (FTB 4600)

The FTB 4600 is the Franchise Tax Board telling you they believe you had California income in a specific tax year but never filed a California return. The FTB uses income data from employers, banks, federal tax return information, and other sources to identify people who may owe California tax but didn’t file. You typically have 30 days from the notice date to either file the missing return or explain why you weren’t required to file.

California’s filing requirement for the 2024 tax year kicks in at $17,029 in gross income for single filers under 65, with different thresholds for married, head of household, and senior filers. If you earned more than those amounts from California sources — even temporarily as a part-year resident or nonresident — you likely had a filing obligation. The FTB’s 4600 notice is based on a calculation that you exceeded those thresholds.

The Reed Corporation responds to FTB 4600 notices by first reviewing the income information the FTB is relying on. If you actually owed a California return, we prepare and file it right away. If you weren’t required to file — because your income was below threshold or because you weren’t a California resident — we prepare a written explanation with supporting documentation.

Ignoring the FTB 4600 is one of the costlier mistakes California taxpayers make. If you don’t respond within the deadline, the FTB will prepare a Substitute for Return (SFR) — their own estimate of what you owed — and issue a Notice of Proposed Assessment based on that estimate. FTB substitutes for returns use the highest standard deduction and filing status and don’t include deductions, credits, or exemptions you would have claimed. The resulting bill is almost always much higher than your actual liability.

On top of the inflated tax estimate, the FTB adds a 25% delinquency penalty under California Revenue and Taxation Code Section 19131, plus daily interest under R&TC Section 19521. If they later determine the failure to file was fraudulent, the penalty jumps to 75% under R&TC Section 19164. These penalties compound quickly — on a $20,000 assessment, you could be looking at $5,000 to $15,000 in penalties and interest before you even dispute the underlying tax.

We have filed returns in response to FTB 4600 notices years after the original due date. Even a late-filed return reduces the assessment to your actual liability and stops the delinquency penalty from growing. The statute of limitations for the FTB to assess additional tax is generally four years from the original due date — but that clock never starts running on a year where no return was filed.

Yes. California has broad authority to compel return filing and assess taxes without your cooperation. If you don’t respond to the FTB 4600 and don’t file, the FTB proceeds with a Substitute for Return under California Revenue and Taxation Code Section 19087. That SFR is treated as an official assessment — the FTB can then use California’s full collection arsenal, including bank levies, wage garnishments, and property liens, to collect the amount they’ve estimated you owe.

There’s another tool in the FTB’s kit that most people don’t know about: the FTB can subpoena your bank records, employment records, and other financial documents directly from third parties without your permission under California Revenue and Taxation Code Section 19504. They don’t need you to cooperate to build a picture of your income. That’s often how they constructed the estimate in the 4600 notice to begin with.

Filing your actual return — even a late one — is almost always better than letting the FTB file a substitute. Your actual return reflects your real deductions and credits. The FTB’s SFR doesn’t. We’ve prepared returns for tax years going back five to ten years when clients received FTB 4600 notices for multiple years and needed to clear up multiple missing filings at once.

Yes, you need to respond — but your response would explain why you weren’t required to file, not submit a California return. California taxes nonresidents on California-sourced income above the filing threshold. If you lived in another state but earned California income from wages, rental property, business operations, or S-corporation/partnership income sourced to California, you may have had a California nonresident filing obligation even without living there.

California also has an aggressive residency audit program. Under California Revenue and Taxation Code Section 17041, California taxes residents on all income regardless of where it’s earned. If the FTB believes you were domiciled in California even though you filed taxes in another state, the 4600 can be the start of a residency determination audit — a much more involved process. The FTB looks at things like where you held a driver’s license, where your vehicles were registered, where your immediate family lived, and the number of days you spent in California.

We handle FTB nonresident responses with a detailed explanation of your domicile and California connections for the tax year in question. If you had California source income, we prepare the nonresident return (Form 540NR) for any year where income exceeded the threshold. If you were a full nonresident with no California source income, we prepare a written response explaining that position and supporting it with documentation.

For a year where no return was ever filed, the California FTB’s ability to assess tax never expires — there’s no statute of limitations when a return wasn’t filed. Under California Revenue and Taxation Code Section 19057, the standard four-year assessment period only begins when a return is actually filed. Skip a year? The FTB can come after you for that year ten or twenty years later if they decide to.

In practice, the FTB focuses most enforcement on the past six to eight years, because older records become harder to reconstruct and the administrative cost-benefit calculation shifts. But that’s not a rule you can rely on — the FTB can and does pursue old unfiled years when the amounts are significant. If you have W-2 or 1099 income reported to California for an unfiled year, those records are likely sitting in the FTB’s database waiting to be used.

The best way to close out old unfiled California years is to file the returns — even very late — before the FTB comes to you. Once you file, the four-year assessment clock starts and the FTB’s window to audit those returns is limited. We’ve prepared returns for clients covering California filing gaps spanning a decade, often finding that the actual liability was a fraction of what the FTB’s estimates suggested.