Electronic monitoring was introduced in 1999 to support the police, courts, prisons and wider justice system in England and Wales.

It is a way of remotely monitoring and recording information on an individual’s whereabouts or movements, using an electronic tag which is normally fitted to a subject’s ankle. The tag transmits this information, via a base unit installed in a subject’s residence, to a monitoring centre where it is processed and recorded in case management systems. Staff in the monitoring centre review this information to see whether an individual is complying with the conditions of their curfew or other electronically monitored requirement. Where a subject is not complying, the electronic monitoring provider either acts on this information themselves or provides it to the relevant authority to take the necessary enforcement action.

The figures for 31 March 2019 include details of those on location monitoring tags, which were introduced in November 2018.