Estimated tax payment after Roth conversion in 1st quarter, 2025

Hello,

Our joint filing tax bracket is 24%. We did Roth conversion ($100000) earlier this year. Paid 24% ($24000) estimated tax before 4/15 deadline. We are planning to do more conversion (maybe about $40k) later this year. Then pay another 24% estimated tax for that amount before 1/15/2026 deadline. We do not quite understand the safe harbor rule. Should we pay some taxes in 2nd/3rd Quarter to avoid penalties? How much should we pay to avoid penalties?

Thanks,

posted