Published 2026-08-24

Roth Conversions: Irreversible Since 2018, and Four Things to Check First

Moving pre-tax retirement money into a Roth means paying the tax now to stop paying it later. The arithmetic is simple and the traps are not — and unlike almost everything else in the tax code, you cannot undo it.

By Victor Gil Vazquez

6 min read

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Key takeaways

The converted amount is taxable income in the year you convert. There is no income limit on converting.
Recharacterisation is gone. The IRS is explicit: no recharacterisations of conversions made in 2018 or later.
The pro-rata rule means you cannot convert only your after-tax money if you hold any pre-tax IRA balance.
The tax is best paid from outside the retirement account. Paying it from the conversion defeats most of the point.

The short answer

A Roth conversion moves money from a traditional IRA or a pre-tax employer plan into a Roth IRA. You pay income tax on the amount converted this year, and in exchange that money — and everything it earns afterwards — comes out tax-free in retirement.

It makes sense when you expect your tax rate in retirement to be higher than it is today, or when you want to remove the future required minimum distributions that a traditional balance eventually forces on you.

It makes less sense when converting pushes you into a higher bracket now, when you would have to pay the tax out of the converted money itself, or when you will need the money within five years.

None of this is tax advice for your situation. The conditions below decide the answer, and several of them depend on figures only your own return will tell you.

The rule that makes this different: you cannot undo it

Until 2017 a conversion could be recharacterised — reversed, as if it had never happened — which meant you could convert early in the year and unwind it if the market fell or the tax bill turned out worse than expected.

That is over. IRS Publication 590-A states it plainly: no recharacterisations of conversions made in 2018 or later. The Tax Cuts and Jobs Act removed the option, and it has not come back.

The practical consequence is that the modelling has to happen before, not after. A conversion done in January on an assumption about the year's income is a bet you cannot settle in December.

The IRS publication this comes fromPublication 590-A covers contributions and conversions to IRAs, including the recharacterisation rule and the ordering of taxable amounts.

The pro-rata rule, and who it catches

This is the trap that surprises people who thought they had found a loophole. If your traditional IRAs contain both deductible (pre-tax) and non-deductible (after-tax) money, you cannot choose to convert only the after-tax part.

Every conversion draws proportionally from both, based on the ratio of after-tax basis to your total balance across all traditional, SEP and SIMPLE IRAs — measured at year end, not on the day you convert. Convert $7,000 when 90% of your IRA money is pre-tax, and 90% of that conversion is taxable, whatever account it physically came from.

It also applies across accounts you might think of as separate. The rule aggregates all of your traditional IRAs into one pot for this calculation, which is why a large rollover IRA from an old employer plan can make an otherwise clean conversion expensive.

Worked example of the pro-rata rule — illustrative figures
	Amount
After-tax basis across all traditional IRAs	$7,000
Total balance across all traditional IRAs	$70,000
Share that is after-tax	10%
Amount converted	$7,000
Of which tax-free	$700
Of which taxable income this year	$6,300

Worked example of the pro-rata rule — illustrative figures

The five-year clocks — there are two

People say 'the five-year rule' as though there is one. There are two, they run separately, and they answer different questions.

The qualified distribution clock: five years from your first contribution to any Roth IRA, which together with being over 59½ makes earnings tax-free. One clock, per person, and it starts once.
The conversion clock: five years from each conversion, before which withdrawing that converted amount under 59½ can trigger a 10% penalty — even though the tax on it was already paid. Each conversion starts its own.

Why the two clocks are separatePublication 590-B sets out the ordering of Roth distributions and the five-year periods that govern them.

The four things to check before converting

Each of these can turn a good conversion into a costly one, and none of them shows up in the headline arithmetic.

Where the tax gets paid from. Paying it out of the conversion itself shrinks the balance that was going to grow tax-free, and under 59½ the withheld amount can itself be treated as a distribution with a penalty. Converting is most efficient when you have taxable savings to pay the bill.
What it does to your bracket. Converted income stacks on top of everything else you earn that year. Converting up to the top of your current bracket, rather than all at once, is the usual way to avoid paying a higher marginal rate on the last slice.
Medicare premiums, if you are near 63 or older. Part B and Part D surcharges are set from your income two years earlier, so a conversion at 63 can raise the premium at 65. It is a cliff rather than a slope — a dollar over a threshold moves the whole bracket.
Marketplace health insurance subsidies, if you buy your own cover. Premium tax credits are calculated from income, and a conversion can reduce or eliminate them for that year.

The account this is moving money intoTraditional and Roth compared on the one axis that decides it: whether you pay the tax now or later.

When it tends to be worth it

There is a shape to the years in which conversions pay off, and it is mostly about a temporarily low tax rate.

A gap year: unemployment, a sabbatical, the first year of a business, or early retirement before pensions and Social Security start.
Between retiring and starting required minimum distributions, when income is low and the future RMD is large.
When the market has fallen and the same shares convert for a smaller taxable amount.
When leaving money to heirs matters. A designated beneficiary who is not an eligible designated beneficiary has to empty an inherited IRA within ten years — and a Roth lets them do that without an income tax bill. The exempt group is narrower than people assume: a surviving spouse, a minor child of the owner, someone disabled or chronically ill, and anyone not more than ten years younger than the owner.

Where the retirement accounts sit relative to each otherThe employer match first, then the tax-advantaged accounts in order. A conversion is a decision about money that is already inside one of them.

Frequently asked questions

Is there an income limit on converting?

No. Direct Roth contributions are limited by income; conversions are not. That asymmetry is why the strategy exists at all.

Can I undo a conversion if it turns out badly?

No. IRS Publication 590-A states that there are no recharacterisations of conversions made in 2018 or later. This is the single most important difference from how the rule worked before the Tax Cuts and Jobs Act.

Does a conversion count toward my annual contribution limit?

No. A conversion is not a contribution, and the two limits are separate. You can convert in the same year you contribute.

Should I convert everything at once?

Rarely. A large conversion stacks on your other income and can push the last part of it into a higher bracket, and near retirement age it can also trigger Medicare surcharges. Spreading conversions across years is the common approach, and the right size depends on figures only your own return shows.

Run the numbers

This guide explains the concept. These put your own figures on it.

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Terms used in this guide

Traditional vs Roth: Two ways of getting the tax break. A Traditional IRA may cut your taxable income the year you pay in, and you are taxed when you take it out. A Roth is paid in with money already taxed, and qualified withdrawals come out untaxed.
Contribution limit: The most the IRS lets you put into a retirement account in one tax year. It is a combined ceiling across your Traditional and Roth IRAs, not one limit each, and it changes most years.
Catch-up contribution: An extra amount the IRS lets you add on top of the normal limit once you reach a qualifying age. It replaces nothing — it is added to the standard limit for that year.

Sources

Internal Revenue Service — Publication 590-A — contributions to individual retirement arrangements, including conversions and the recharacterisation rule
Internal Revenue Service — Publication 590-B — distributions from individual retirement arrangements, including the five-year rules
Internal Revenue Service — Roth IRAs — overview and limits
Social Security Administration — Request to lower an Income-Related Monthly Adjustment Amount (IRMAA) — the surcharge is set from the return filed two years earlier

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