Various haredi and hasidic yeshivas in Rockland County, New York allegedly have set up their own currency systems and 'banks' so teachers and other employees can receive much of their salary off the books.
A Rockland County source writes:
State and federal money that goes into the yeshivas are exchanged into vouchers used to, among other things, pay staff (especially in New square), who in turn use this as an underground currency. It's a complex system that operates very murkily. New Square has its own undocumented cash bank where cash deposits can be exchanged for vouchers to be used in stores in the community.…
Here is an alleged example of one of those haredi private currency systems. (I don't have any firsthand information confirming that what this particular yeshiva is doing is illegal or dishonest, but this is what these haredi yeshiva vouchers sometimes look like.)
Please click to enlarge: