If you’re thinking of converting all or part of a traditional IRA to a Roth… Know that Roth conversions done after 2017 are irreversible. Prior to 2018, you had until Oct. 15 of the year following the conversion to undo the switch and eliminate the tax bill by transferring the funds back to a traditional IRA. This is called a recharacterization and could make sense if the Roth lost money. President Trump’s tax reform law eliminated recharacterizations of Roth conversions. You can still convert your IRA to a Roth, but you won’t be able to undo it later.