My wife has an old IRA as well as a Roth IRA with the same large broker. I'm thinking of doing a Roth conversion on this IRA. I'd like to pay these taxes with some funds I have in a non retirement account. How does this work? Do I just send the government a check? Will waiting until the 4th quarter make it easier?
I have done a couple of Roth conversions. One year I made an estimated tax payment in December (1040-ES). The other time I didn't send any tax payment for it. I just let my typical overpayment of taxes from a W-2 job pay it. I ended up with a much smaller refund when I did that year's taxes.
Personally, I would not take money out of the conversion to pay taxes. My preference is to come up with tax money from other savings. I feel that is better because I don't want to over estimate the tax, which essentially converts IRA money into refund money.
If either of you have a W-2 job, consider adjusting your witholdings to take out extra money each paycheck. Tax payments are fungible, so it doesn't really matter who pays them.
Lastly, you might want to research the rules for when underpayment of taxes results in a penalty. You could skip the tax payment for now if you know you won't be penalized next April. You should be clear if your witholdings will add up to at least 90% of the total tax due this year, but do your own diligence.
H