"Our 2-year investigation has concluded that Block has systematically taken advantage of the demographics it claims to be helping," the short seller said in its report.
Up to 35% of Cash App's revenue is derived from interchange fees, Hindenburg alleged.
But Block avoids that regulatory cap imposed on large financial institutions by routing the revenue through a small bank, Hindenburg alleged.
The small-bank routing method is one employed by Block rival PayPal , the short seller claimed, and which prompted a Securities and Exchange Commission probe.
Hindenburg took issue with Cash App's practices during the pandemic, when the government issued stimulus checks to qualified American adults.