After you file

Tweak to "Note that IRA withdrawals are considered to have been distributed equally during the year even if you withdrew it all in December."

 

Conversions are not withdrawals or distributions and are considered taxable in the quarter they occur. 

 

Now if you have distributions then those are considered distributed equally during the year and that includes  any withholdings you have taken even if the entire distribution is done on 12/31.