How do you intend to "apply" the distribution to your taxes? Using the money to make a 4th quarter estimated tax payment in January, or try and have the entire amount withheld by the custodian? The latter credits the payment evenly over the 4 quarters in the "first cut" calculation while the former credits the payment entirely to the 4th quarter.
Can you apply the RMD to federal taxes? Of course you can.
Should you apply the RMD to federal taxes? That's one of those "it depends" sort of answers. I assume the underpayment penalty is the unstated focus of your question? You'd have to sit down and run the numbers to answer that, using both the "normal" calculation and then again by "annualizing."
