Used to intensively monitor a small number of subjects including: some of the highest risk offenders managed under Multi-Agency Public Protection Arrangements (MAPPA); those granted bail by the Special Immigration Appeals Commission (SIAC); and those made subject to Terrorism Prevention and Investigation Measures (TPIMs). In these cases, monitoring may be by way of a Global Positioning System (GPS) tag rather than a radio frequency (RF) tag.

The data source for this measure is HM prison and probation service annual digest.