Retirement tax questions

If you do a conversion in January 2025, the IRS will want to see the estimated taxes either paid all at once (no later than April 15, 2025) or in 4 equal installments due April 15, June 15, Sept 15, and January 15, 2026.  If you don't make the estimated payments, you can be assessed an underpayment penalty even if you pay in full when you file your 2025 tax return in April, 2026.