Meet Alice. Alice knowingly made false reports to the police. For how long after this occurrence may this crime be reported and proceeded against Alice for?
If the offence is considered to be a summary only offence such as Obstructing a Police Officer, s89(2) Police Act 1996, or Wasting Police Time, s5(2) Criminal Law Act 1967, then the complaint becomes time-barred six months after the alleged offence occurred.
These are heard by magistrates' court and s127(1) of the Magistrates' Court Act 1980 says:
Except as otherwise expressly provided by any enactment and subject to subsection (2) below, a magistrates’ court shall not try an information or hear a complaint unless the information was laid, or the complaint made, within 6 months from the time when the offence was committed, or the matter of complaint arose.
If the offence is a more serious offence, e.g. Assisting an Offender, s4(1) Criminal Law Act 1967 (i.e. lying to the police to protect the offender), or Perverting the Course of Justice, then there is no such time limit.