December IRA to Roth Conversion & 60-Day Rollover

Looking for some clarification.  My 2025 MAGI will be over $260k once I complete a $40k Roth conversion this month (Dec 2025).  If I withhold 24% of the conversion, only $30,400 rolls into my Roth and the remaining $9600 pays the federal taxes.  Some questions:

  1)  I'm assuming since I do a withholding, there's no underpayment penalty?  Am I correct?

  2)  Can I then use my separate savings account to put $9600 into the Roth (60-day rollover) and not incur any penalty?  This way, I get the full $40k into the Roth.

  3)  Is that $9600 capped because my MAGI is large this year?  In other words, is the $9600 considered a Roth contribution, rollover, or what is it actually?  I think it's a rollover because I'm assuming the 60-day rollover allows this, but this is where I get confused.  

  4)  How will TT treat the $9600 rollover?  There's no document because I'll be using my bank account.  

 

I do realize this rollover strategy is only allowed once in 12 months.  I didn't do this last year so I think I'm good there. 

 

Many thanks to all!!