This?

https://www.onwallstreet.com/news/new-tax-bill-no-more-roth-ira-do-overs

New tax bill: No more Roth IRA do-overs

As it’s being hashed out, the new tax bill contains an unexpected and not widely publicized provision: The repeal of the Roth conversion do-over, also known as a Roth recharacterization.

This marks the end of the so-called Roth conversion cycle where funds could be converted to a Roth IRA, and then all or any part of that conversion could be undone or recharacterized.