I'm glad you posted your affirmative reply about paying the taxes on a Roth conversion in the quarter it is done. I saw the same quote/source when searching "When do I owe taxes on my Roth conversion?" The person who gave the advice about it not being due until you file your taxes was a CPA with a financial investment firm, so I'm scratching my head about that. Perhaps they were quoted out of contest.
They did refer to the safe harbor rule. Do you find that valid for Roth conversions? That is, for example, say you are doing one for the first time and your current withholding + any quarterly equable estimated tax payments cover your liability for the previous year's filing, could you pay the additional tax owed on the Roth conversion at filing time?
