@Matt18 I've been doing Roth conversions for the past three years and had variable income, so I hear what you're saying. I do estimated tax payments for the first three quarters, not including Roth conversion, do my Roth conversion in the last quarter, then my last quarterly payment on Jan 15th includes taxes for the Roth conversion. I do file Form 2210 to avoid a penalty. Safe harbor strategy wouldn't work for me because I don't know for certain how much or if I'm going to do a Roth conversion until the end of the calendar year. One Turbotax tool that has proven invaluable to me in calculating my quarterly estimates is the What-if worksheet, it's available with the CD version. Whenever a quarterly estimate deadline comes up I bring up the What-if and recalculate my quarterly taxes due. It's also helpful in playing out different scenarios with various Roth conversion amounts.
