The IRS has provided an update on its website regarding Roth recharacterizations in its FAQ section. As you know, this option to recharacterize your Roth IRA was eliminated with the passing of the new Tax Cuts and Jobs Act.
The IRS clarified that if you did a Roth conversion in 2017, you may still be eligible to recharacterize it as long as it is done by October 15, 2018.
Keep in mind that any Roth conversions done January 1, 2018 and on, are not eligible for recharacterization.
Source: www.irs.gov