What happens when a Contractor fails to pay their remuneration? What happens when a Contractor fails to pay their remuneration? Do they lose their ability or what?
Although this payment can be delayed, especially in the midst of
  combat, it is ultimately unavoidable. It is unknown what happens to a
  Contractor that fails to pay his obeisance, although Amagiri has
  stated that Contractors who fail to do so seemingly 'melt like butter'
  when depriving a captured November 11 of his remuneration.


Taken from: http://darkerthanblack.wikia.com/wiki/Obeisance

(It was also a pretty easy google search)