Retirees who want to turn part of a traditional IRA into a Roth IRA for 2026 have to finish the move by Dec. 31. An ordinary IRA contribution can wait until the April 15 filing deadline, but a conversion counts for the year the money actually moves. Once it is done, the IRS does not let anyone reverse it.

April 15 is for contributions, not conversions

Many savers carry a spring deadline in their heads, and for good reason. Contributions to an IRA for a given year can be made during that year or up to the filing due date, and that is the rule most people have used for decades.

The IRS spells it out in Publication 590-A: for most people, contributions for 2025 had to be made by April 15, 2026. That date has nothing to do with a Roth conversion.

A conversion follows a different clock. The instructions for Form 8606, the form that reports conversions, tell anyone who “converted an amount from a traditional IRA to a Roth IRA in 2025” to file the form for that year. The year of the conversion is the year it was made. Waiting until spring does not move it back into the year before.

That turns a tax question into a calendar question for retirees. The choice is whether to convert some money this year at all, and if so, whether the paperwork can finish in time. Anyone with a traditional IRA at a bank, a brokerage or a fund company has to instruct that custodian early enough for the money to settle by Dec. 31. A conversion that has not gone through by then belongs to 2027, not 2026.

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The IRS counts the year a conversion is made, not the day a request is sent. Each custodian sets its own processing times, so a request filed in the last days of December carries a real risk of landing on the wrong side of New Year’s Day. The safe course is to ask now, while there is room in the calendar.

Why a Roth conversion cannot be undone

The Form 8606 instructions are blunt on this point. A conversion of a traditional IRA to a Roth IRA made in tax years beginning after Dec. 31, 2017, “cannot be recharacterized as having been made to a traditional IRA.”

It was not always so. The IRS’s IRA questions and answers note that a conversion made in 2017 could be recharacterized if that was done by Oct. 15, 2018. Conversions on or after Jan. 1, 2018, cannot. Retirees who remember undoing a conversion after a market drop are remembering a rule that has ended.

The agency repeats the point on its Roth IRA contributions page, updated Sept. 24, 2026. It says conversions after 2017 from a traditional IRA to a Roth IRA may not be recharacterized. Ordinary Roth contributions can still be recharacterized in some cases; conversions cannot.

What the IRS counts as taxable

The IRS says a conversion “results in taxation of any untaxed amounts in the traditional IRA.” In plain terms, pre-tax money that moves to a Roth is added to income for the year of the conversion. Because the move cannot be recharacterized, that amount stands even if the account falls in value afterward.

Line 8 of the Form 8606 instructions asks filers to enter the net amount converted during the year, and Part II of the form is built around those conversions. The instructions list anyone who converted an amount during the year among those who must file, so a conversion finished in the last week of December still shows up on the 2026 return that is due in the spring of 2027. The same tax-topic page says a traditional IRA can be converted to a Roth regardless of income, so there is no earnings cap to clear first.

The IRS rollover rules add two details. Its rollover page says the one-rollover-per-year limit does not apply to conversions, so more than one can be made in a year. It also says that someone who takes a distribution has 60 days to roll it over, and any amount not rolled over is taxable.

The 2027 brackets are not out yet

A conversion is usually sized against a tax bracket, and that is where the timing gets tricky. As of Oct. 29, the IRS newsroom had not posted the 2027 tax brackets. That means the 2026 brackets can be measured today, while a plan built around 2027 has to wait for numbers the agency has not released.

The open question for each retiree is whether to fill room in a 2026 bracket now, knowing the conversion is final and the money must settle by Dec. 31, or to hold off and decide under the 2027 numbers once they appear. The IRS rules do not answer that. They only fix the date and the finality.

Weighing a conversion before the year closes?

A conversion that slips past Dec. 31 lands in 2027, and one that overshoots the bracket cannot be recharacterized afterward. Both mistakes are permanent, and both are easy to make with a few days left.

The Roth Conversion Window is a 16-page guide built around “filling the bracket, and stopping at the line.” It includes a room finder and a multi-year planner worksheet for working out how much of an IRA fits in a bracket each year.

Get the Roth conversion bracket guide for the Dec. 31 cut-off →

This article was produced with AI assistance and edited for accuracy against the sources linked above.