California FTB Notice Reported Income (FTB 4660 ENS)

The FTB 4660 ENS is a Reported Income notice from the California Franchise Tax Board, similar in purpose to the FTB 4108 ENS. Both notices alert you to income the FTB has on record that doesn’t match your filed California return — or that relates to a year where you haven’t filed. The 4660 ENS is typically used for a different category of income types or a different stage in the FTB’s automated matching process. The FTB uses different form numbers to target specific income categories, taxpayer types, or notice sequences within their Automated Underreporter (AUR) program.

The ‘ENS’ suffix on both notices indicates employer notification was also sent, meaning the payer that reported the income to the FTB received a copy or notification as part of the process. This is relevant because your employer or payer may ask you about the notice or may have already provided additional information to the FTB through their own response to a related inquiry.

The core obligation is the same regardless of form number: respond within the stated deadline, account for the income the FTB has listed, and either file an amended return or explain why the income wasn’t taxable on your California return. The specific form number helps identify what triggered the notice, which informs the appropriate response.

The FTB 4660 ENS can be triggered by several income categories that the FTB’s automated matching system flags. Retirement distributions reported on 1099-R forms are a frequent source, particularly early distributions that were rolled over (and so not taxable) but were reported as distributions without the rollover indicator. Stock compensation income — like restricted stock units (RSUs) and non-qualified stock options (NQSOs) — is another common trigger, since the W-2 Box 12 or Box 14 amounts don’t always get correctly cross-referenced against the California Schedule S or NR.

Miscellaneous income from platforms like Airbnb, Etsy, or other gig economy operators now gets reported on 1099-K forms once you exceed $5,000 in gross payments (under IRS Notice 2024-85, the $600 threshold is being phased in). If your California return didn’t include this income, or if you reported a lower net amount without explanation, the FTB’s automated systems can flag it and generate a 4660 ENS. Similarly, gambling winnings on W-2Gs are commonly underreported.

Partnership and S-corporation income flowing through Schedule K-1 is also a trigger when the K-1 income doesn’t appear on a California return. The FTB receives copies of California partnership returns (Form 565) and S-corp returns (Form 100S), which show each partner’s or shareholder’s distributive share. If that income isn’t on your personal return, expect a notice.

Not all income reported to the FTB is automatically taxable on your California return — and this is an important distinction when responding to the FTB 4660 ENS. Income that’s taxable federally may receive different treatment in California. For example, California doesn’t conform to federal law on certain exclusions and deductions. On the other hand, some income excluded federally is taxable in California — like unemployment compensation, which California taxes in most cases even though some states don’t.

Common sources of genuine California non-taxability include: IRA-to-IRA rollovers reported as distributions on 1099-R but properly excluded from income, Social Security benefits (California doesn’t tax Social Security, unlike the federal government), interest from U.S. government obligations (exempt in California even though taxable federally), and income earned by a nonresident outside California that gets reported to California by a payer headquartered in the state.

If you’re a nonresident or part-year resident, California only taxes your California-source income — income earned from work physically performed in California, California rental properties, or California business operations. A 1099 for out-of-state work showing your California home address doesn’t automatically make that income California-taxable. We review the sourcing rules carefully before conceding that income is taxable when the FTB assumes it is.

The FTB 4660 ENS states a specific response deadline, typically 30-60 days from the notice date. This deadline is meaningful — missing it allows the FTB to proceed with a Notice of Proposed Assessment based on their records alone. Under Revenue and Taxation Code Section 19087, the FTB can propose an assessment of additional tax when they determine your return understated income. Without your input, the assessment is based on gross income with no credit for your deductions or credits.

If you miss the deadline, you haven’t permanently lost your rights. You can still respond after the deadline and request that the FTB consider your documentation before finalizing an assessment. The FTB generally allows late responses before the NPA becomes final (which occurs 30-60 days after the NPA is issued, depending on the notice type). However, a late response carries more risk because the FTB may have already moved to the next stage.

If a Notice of Proposed Assessment has already been issued because you missed the 4660 ENS deadline, your next formal option is to protest the NPA within 60 days of its issuance under Revenue and Taxation Code Section 19041. The protest lets you present all the documentation you would have sent in response to the original 4660 ENS. Don’t let the NPA become final without responding — once it does, collection begins.

The right approach depends on whether you actually owe additional tax. If the FTB 4660 ENS identifies income you did receive but didn’t report, and that income is taxable in California, filing an amended return (Form 540X) is usually the cleaner resolution. An amended return goes through the FTB’s normal processing, calculates the correct tax with your actual deductions and credits applied, and creates a clear paper trail showing you corrected the issue voluntarily. The penalty treatment for voluntary amendments is also typically better than for FTB-initiated assessments.

If the income isn’t taxable — because of a rollover, nonresident status, or a California-specific exclusion — a written response explaining why the income doesn’t belong on your return is the appropriate path. In this case, you’re not amending because your original return was correct. Your written response should explain the non-taxability, cite the relevant California statute or regulation, and include supporting documentation. A well-structured letter with the right legal support usually resolves it.

When both apply — some of the income is taxable and some isn’t — we typically file an amended return for the taxable portion and include an explanatory letter addressing the non-taxable portion simultaneously. Sending both together is more efficient than a letter that resolves the non-taxable issue and then triggers a follow-up inquiry about the taxable part. The Reed Corporation handles both paths and makes sure whichever route we take includes the documentation necessary to close the issue in one round.