The Tax Math on a California Roth Conversion

When you convert a traditional IRA to a Roth, the entire converted amount is added to your taxable income for the year. In California, that income faces both federal and state tax.

For an LA resident converting $150,000 with $250,000 in other income, the approximate tax hit looks like this:

• Federal income tax on the conversion: roughly $49,500 (32%-35% marginal range per IRS 2025 brackets)
• California income tax on the conversion: roughly $14,000 to $19,950 (9.3%-13.3% depending on total income per FTB rate schedules)

Combined tax on the $150,000 conversion: somewhere around $63,500 to $69,450. That’s 42% to 46% of the converted amount going straight to the IRS and the Franchise Tax Board. It stings.

Why Converting in California Can Still Save You Money

The instinct is to assume you should never convert in a high-tax state. But that logic only holds if you’re planning to leave California before retirement. If you’re staying in LA — and a lot of people do, because it’s hard to leave year-round weather and a career network — then your traditional IRA distributions will face the same California tax rates during retirement.

Consider this: a $500,000 traditional IRA growing at 7% annually for 15 years becomes roughly $1,380,000. The required minimum distributions (RMDs) starting at 73 (under IRC § 401(a)(9)) will force you to pull out about $52,000 in the first year, growing each year after that. All of it taxed at ordinary income rates, including California’s.

If you’d converted that $500,000 over five years ($100,000 per year) in your 50s, you’d have paid California tax on $500,000 total. By not converting, you’ll eventually pay California tax on $1,380,000 or more as it comes out in distributions. The tax rate might be similar, but the dollars are much larger.

The Mental Health Tax Bracket

Here’s a detail that doesn’t show up in tax projection spreadsheets: RMDs from a large traditional IRA can push you into California’s highest brackets during years when you don’t need or want the income. You’ll pay 13.3% on income above roughly $1 million (or $1.4 million married filing jointly for the mental health services tax bracket, which is the additional 1% that takes CA from 12.3% to 13.3%).

A Roth doesn’t have RMDs during your lifetime (per IRC § 408A(c)(5)). Your money grows without being forced out at a pace the government dictates. For high-net-worth Los Angeles residents, this control over timing is often worth more than the up-front tax cost.

Bracket-Filling Strategy for LA Residents

The most common approach we recommend: convert enough each year to fill your current federal and California tax brackets without jumping to the next one.

California’s bracket structure creates some natural breakpoints. The 9.3% rate kicks in at $68,350 for single filers ($136,698 married filing jointly) and stays there until $349,137 ($698,274 MFJ). That’s a wide plateau. If you’re already in the 9.3% bracket from your regular income, you can convert a meaningful amount before hitting the 10.3% rate at $349,137.

The federal brackets matter too. For 2025, filling up the 24% bracket (which ends at $191,950 for single filers, $383,900 MFJ per IRS Rev. Proc. 2024-40) while staying in California’s 9.3% band is the sweet spot for many LA professionals. Total marginal rate: about 33.3%. That’s not cheap, but it’s manageable and likely lower than what you’d pay on forced RMD income in your 70s and 80s.

What If You’re Planning to Leave California?

If a move to Nevada, Texas, Florida, or another no-income-tax state is genuinely on the horizon, waiting to convert makes obvious financial sense. A $300,000 conversion done in LA costs roughly $28,000 to $40,000 in California state tax alone. Do it after establishing residency in Las Vegas and that cost drops to zero.

But “planning to leave” and actually leaving are different things. We’ve seen clients delay conversions for five or six years waiting for a move that never happens. Each year they wait, the traditional IRA grows, and the eventual tax bill gets larger. If you’re not moving within 12 to 18 months, start converting in California rather than waiting indefinitely for a move that might not materialize.

California’s residency rules are strict. The Franchise Tax Board looks at where your home is, where your spouse and children live, where you’re registered to vote, and where you spend your time. A P.O. box in Reno doesn’t make you a Nevada resident.

Estimated Payments and Timing

Roth conversions don’t come with automatic withholding unless you request it. For California filers, that means you’ll owe estimated payments to both the IRS (Form 1040-ES) and the FTB (Form 540-ES).

If you convert early in the year, spread your estimated payments across the remaining quarters. Late-year conversions — common in December when you have a clearer picture of your annual income — require a large Q4 payment by January 15 to avoid underpayment penalties. Your CPA should model both the conversion amount and the estimated payment schedule together.

Sources

• IRS — Required Minimum Distributions
• 26 U.S.C. § 408A — Roth IRAs (Cornell Law)
• California Franchise Tax Board — Personal Income Tax Rates
• IRS — 2025 Tax Inflation Adjustments (Rev. Proc. 2024-40)
• FTB — California Residency Status Rules