In a qui tam action, sometimes called a "whistleblower" action, a private party claims damages on behalf of the government when a person or company is believed to have violated the law or defrauded the government and the government has been harmed.

The government decides whether to participate in the case, and if the case succeeds the private party can recover part of the proceeds.

Qui tam actions can be filed on behalf of either the federal or the state government.