Reports made to the police are considered privileged, which means that no civil action can arise from the report unless it can be shown that the report was made with actual malice (with a knowledge that the report was false when it was made). Actual malice is difficult to prove, so most false reports will go unpunished.
That said, if the police have to expend a lot of time and resources investigating a report that later turns out to be false, there are criminal penalties that can be imposed on the false-reporter. This is most often the case in false reports of kidnappings or rapes or child-related crimes or reports of that nature.
For example, charges were filed against the parents of "balloon boy," after it was discovered (thanks to statements made by the boy) that the report of the runaway balloon with the boy inside was just a publicity stunt.
The reason why police reports (and reports to CPS) are covered by privilege is to allow for the unfettered reporting by citizens of crimes or suspected crimes without fear that the citizen-reporter will face a lawsuit should the report turn out to have no merit. The names of the reporters of crimes are generally kept confidential, unless there is a court order that demands disclosure.
Police reports are not considered true or false, by the way. It takes a police investigation to determine their truth or falsity. If false, the matter is generally dropped. If the report is found to have some merit, and the person reported is charged with a crime after a police investigation, there has been enough evidence found to support the charges.