The tax reform bill has removed the ability to recharacterize any Roth IRA conversions done in 2018 and onward.
https://www.irs.gov/retirement-plans/ira-faqs-recharacterization-of-ira-contributions
https://www.forbes.com/sites/jamiehopkins/2018/01/04/tax-reform-changes-to-recharacterizations-and-r...
