The black market, underground economy, or shadow economy is a clandestine market or transaction that has some aspect of illegality or is characterized by some form of noncompliant behaviour with an institutional set of rules.


Because tax evasion or participation in a black market activity is illegal, participants will attempt to hide their behaviour from the government or regulatory authority. Cash usage is the preferred medium of exchange in illegal transactions since cash usage does not leave a footprint. And the preferred currency is US$