6 Things to Understand About a Roth Conversion Before You Do One

6 Things to Understand About a Roth Conversion Before You Do One

A Roth conversion is one of the few moves in personal finance that is genuinely irreversible.

Not "hard to undo." Irreversible. The ability to recharacterize a conversion, which used to function as a legal undo button, was eliminated by the 2017 tax law for conversions made after December 31, 2017. Whatever the market does in the following six months, the tax bill stands.

So it is worth understanding a Roth conversion before you do one rather than in the following April. Here are the six mechanics that decide whether it works, none of which is an argument for or against doing it in your situation.

1. The Converted Amount Is Ordinary Income This Year

A conversion moves money from a pre-tax account to a Roth account and reports the pre-tax portion as ordinary income in the year of the conversion.

It stacks. It does not sit in a separate bucket with its own rate. It sits above your wages, your business income, your interest, and your capital gains, and it can push the last dollars of the conversion into a higher marginal bracket than the first dollars.

The planning question is therefore not "should I convert" but "how much fits under a specific threshold this year." That threshold might be a bracket ceiling, an income phase-out you want to stay under, or a cliff described below.

What that buys, in theory, is tax-free growth and no required minimum distributions from the Roth IRA during the original owner's lifetime. What it costs is certain, immediate, and paid in cash. The benefit is projected. The cost is not.

2. The Pro Rata Rule Treats All Your IRAs as One Account

This is where the do-it-yourself version most often goes wrong.

Under IRC Section 408(d)(2), all of your traditional, SEP, and SIMPLE IRAs are aggregated and treated as a single account when determining how much of a distribution or conversion is taxable. You cannot convert the after-tax money and leave the pre-tax money behind.

The mechanics: taxable portion equals the conversion amount multiplied by the pre-tax share of your total IRA balance. If 90% of your combined IRA balance is pre-tax, then 90% of any conversion is taxable, no matter which specific account the money left.

The classic failure is the backdoor contribution. Someone makes a $7,000 non-deductible contribution, converts it, expects a tax-free conversion, and has a $400,000 rollover IRA sitting in the same aggregation pool. Almost all of that conversion is taxable, and the after-tax basis they thought they used is still stranded.

Employer plan balances are generally outside the IRA aggregation, which is why some people roll an IRA into a current 401(k) before converting. Whether that is available or advisable depends on the plan document and on facts a professional needs to see.

3. It Cannot Be Undone

Worth repeating as its own point, because it changes how you should time one.

Before 2018, a common approach was to convert early in the year and recharacterize by the extended due date if the market fell or the tax math changed. That option is gone.

The practical consequence is that a conversion done in January is a bet on what your full-year income will be. A conversion done in November or December is a calculation based on income you can mostly see. That is a real argument for converting late in the year, and the counterargument is that you give up months of potential tax-free growth. Neither is obviously right, and the answer depends on how predictable your income is.

4. There Are Two Different Five-Year Clocks

People conflate these constantly, and they do different things.

The first clock governs whether earnings come out tax-free, through the qualified distribution rules of IRC Section 408A(d)(2). It starts with your first contribution to any Roth IRA and, once satisfied, is satisfied for good.

The second clock applies to each conversion separately, under IRC Section 408A(d)(3)(F), which applies the Section 72(t) additional tax to converted amounts withdrawn too soon. Withdraw converted principal within five years of that conversion and, if you are under 59 and a half, a 10% additional tax can apply to the amount that was taxable on conversion, even though you already paid income tax on it. Each conversion carries its own clock, running from January 1 of the year of that conversion.

For someone converting in their sixties, this is usually a non-issue. For someone converting at 50 and planning to spend the money at 53, it is the whole issue.

5. The Second-Order Effects Land Later and Elsewhere

A conversion raises this year's modified adjusted gross income, and several things you may not be thinking about are keyed to that number.

Medicare IRMAA surcharges. Part B and Part D premium surcharges are determined from income two years prior. A conversion at 63 shows up as a higher Medicare premium at 65. These are cliffs, not phase-ins: one dollar over a threshold moves the entire surcharge to the next tier.

Marketplace health insurance credits. For anyone buying coverage on an exchange before Medicare, a conversion can reduce or eliminate a premium tax credit. For early retirees this is frequently the largest hidden cost of a conversion, and it is easy to miss because it shows up as a smaller subsidy rather than a bigger bill.

Taxation of Social Security benefits. More income can increase the share of benefits that is taxable, which is why some households do most of their converting in the window between retiring and claiming.

Capital gains rates and net investment income tax. Conversion income does not itself get taxed as capital gain, but it raises the income figure that determines which capital gains rate applies to your other holdings and whether the 3.8% net investment income tax reaches them.

None of these are reasons not to convert. They are reasons the calculation has to include more than a bracket table.

6. Where the Tax Payment Comes From Usually Decides Whether It Works

If you convert $100,000 and pay the resulting tax out of the converted funds, you have moved less than $100,000 into the Roth and, if you are under 59 and a half, the withheld portion is generally treated as a distribution that can carry its own 10% additional tax.

Paying the tax from taxable savings outside the retirement accounts keeps the full amount compounding tax-free and is the version of the strategy the projections usually assume.

Which means the honest precondition is having cash outside the account to pay a tax bill that could be substantial. If you do not, the case for converting weakens considerably, and that is a reasonable place to stop and decide the answer is not now.

Getting a Second Opinion on the Numbers

A conversion analysis is a projection built on assumptions about future tax rates, future returns, and how long the money sits. Change any one of them and the answer can flip. That is not a knock on the analysis. It is the reason to see the assumptions written down rather than accepting a conclusion.

Anthony Syracuse, CFP is a Scottsdale, Arizona advisor, founded in 2022, offering fee-only fiduciary planning with no asset minimums, serving clients nationwide. The stated focus is tech professionals, creatives, and business owners, with high net worth individuals listed as a specialty. Credentials shown on the profile are self-reported and verified by Sam's List against public databases where applicable.

Anthony Syracuse has 5 verified client reviews on Sam's List as of 2026-09-06. Each review is submitted by an individual who identifies as a client of the firm and rates it on communication, subject-matter knowledge, and overall satisfaction. Reviews reflect those individual experiences, do not represent an endorsement by Sam's List, and are not indicative of future results.

A fee-only structure means compensation comes from the client rather than product commissions, which removes one conflict. It does not remove all of them, it does not make any particular recommendation correct for you, and reviews describe other people's experiences rather than predicting yours. Verify any adviser's registration and disciplinary history independently before engaging.

You can compare fee-only planners and read verified client reviews in the Sam's List financial advisor directory.

Frequently Asked Questions

Can a Roth conversion be undone? No. Recharacterization of a Roth conversion was eliminated for conversions made after December 31, 2017. Once the conversion is complete, the income is reported for that tax year regardless of later market moves. Recharacterization of a regular annual contribution between traditional and Roth is a separate rule and still exists.

How does the pro rata rule work for a Roth conversion? All traditional, SEP, and SIMPLE IRAs are aggregated under IRC Section 408(d)(2) and treated as one account. The taxable share of a conversion equals the conversion amount times the pre-tax portion of that combined balance. You cannot isolate after-tax basis and convert only that, which is what defeats many backdoor contribution attempts.

Does a Roth conversion affect Medicare premiums? It can. Income-related monthly adjustment amounts for Medicare Part B and Part D are based on modified adjusted gross income from two years earlier, and they operate as tiers rather than a gradual phase-in. A conversion at age 63 can therefore raise premiums at 65, and crossing a threshold by a small amount moves the whole surcharge tier.

When is a Roth conversion generally considered? It is most often examined in years when income is unusually low relative to expected future income, such as between retirement and the start of Social Security or required minimum distributions, and when cash is available outside retirement accounts to pay the tax. Whether it makes sense for you depends on your bracket now versus later, your time horizon, and your other income-linked benefits, which is a professional analysis rather than a rule.

---

About the author: Kimberly Green is the cofounder of Sam's List, where business owners and high earners find vetted CPAs, financial advisors, and fractional CFOs. She's met one-on-one with 400+ financial professionals and writes from the real data behind thousands of client-advisor matches. Ask her anything about finding an accountant - she's heard it all, including the questions people are afraid to ask.