Miller is the deputy commissioner for services and enforcement.
Shulman (pictured) has been IRS commissioner since March 24 2008. IRS commissioners are nominated by the President and confirmed by the Senate for a term of up to five years with their terms ending on November 12 of their final year (November 9 is the last work day of Shulman's term because November 12 is a federal holiday).
The identity of the permanent commissioner will be a decision for either Barack Obama or Mitt Romney after the presidential election on November 6.