Monopoly money

noun4

1. •
   Play money.
2. •
   Money, especially paper money, that is perceived to have little or no value, or to be distributed freely.
3. •
   (slang, disapproving) Banknotes of foreign currency; especially those which are vibrant or flimsy.
4. •
   Money that does not exist; referring to fraudulent record keeping.

   • They did so to conceal the fact that they were playing with Monopoly money—fabricating profits as phony as the pastel-colored money used in the classic Parker Brothers board game. — 2005