Can I undo my Roth IRA conversion in 2018?
The answer is: It depends.
When you convert a traditional IRA to a Roth IRA, you include the value of your traditional IRA, reduced by any nondeductible contributions you've made, in your income for federal tax purposes in the year of the conversion. For conversions prior to 2018, if you subsequently decided to "recharacterize" or undo the conversion for any reason — e.g., the value of your IRA assets declined after the conversion, resulting in a bad tax deal — the IRS would permit you to do so, provided the recharacterization took place in a timely fashion.
For example, assume you converted a fully taxable traditional IRA worth $50,000 to a Roth IRA in 2016. You would have been required to include $50,000 in income on your 2016 federal income tax return. But shortly after the conversion, the value of your Roth IRA declined to $40,000. Suddenly you were faced with the proposition of paying taxes on $50,000, while your Roth IRA was worth only $40,000. Fortunately, you had until your tax return due date (including extensions) to undo all or part of a conversion. So in this example, you would have had until October 15, 2017, to recharacterize the conversion.
Unfortunately, the Tax Cuts and Jobs Act passed in 2017 eliminated the option to recharacterize a Roth conversion, with one exception: If you converted your Roth IRA in 2017 and have since changed your mind, you have until your filing deadline, including extensions (or until October 15, 2018), to recharacterize.
When you recharacterize, you need to withdraw the amount you originally converted, plus any earnings, out of the Roth IRA and transfer it back to a traditional IRA.
If you already paid your taxes for 2017, you'll need to file an amended return to obtain a refund for any
taxes paid on the conversion. An amended return can generally be filed as late as three years after the
original return was filed.
Undoing a Roth conversion can be complicated, so it's probably a good idea to consult your tax professional before taking action.