A document found as part of the work of the Hillsborough Independent Panel shows £14.53 was gathered from the football ground in Sheffield after a terrace crush claimed the lives of 96 Liverpool fans in April 1989.
According to the 1992 South Yorkshire Police document, the money was among unclaimed property in the stadium after the disaster. It was banked according to the procedures in place at the time, the force said.
But campaigners said it was "beyond belief" that police kept the money which, they said, should have been donated to the victims' fund.
Sheila Coleman, from the Hillsborough Justice Campaign, told a national newspaper: "The fact that they decided to keep it, and not even consider donating it to the disaster fund, speaks volumes."