Qui tam is a common law concept according to which the person contributing to the prosecution can be rewarded with a part of the penalty imposed on the guilty party. The name of the concept comes from the Latin phrase qui tam pro domino rege quam pro se ipso in hac parte sequitur , meaning "[one] who files a lawsuit both on behalf of the king and on his own behalf."
Practical modern qui tam implementations give any person who has relevant information - an informant - the right to file a lawsuit on behalf of the state about the misuse of public resources. If the claim is successful, the informant may claim a share of the compensation paid by the defendant. As a rule, the remuneration of the informant is from 15 to 30% of the compensation payments of the defendant.