If you don't pay your taxes by April 15, you will start to accrue Late Payment penalties and interest until you pay your taxes.  You can take your Required Minimum Distribution before the end of the year.  If you choose to wait to pay your tax, be sure to file your tax return or an extension (will give you to October 15 to file), otherwise you will also be subject to a late filing penalty in addition to the late payment penalty and interest.