City of London

Until recently, collar numbers consisted of a number followed by a single letter to indicate the division (e.g. "PC 123A").^{[citation needed]}

In 1914, the force was reorganised into four divisions, each named after its police station:

Moor Lane Police Station was destroyed in the Blitz in 1940, and A Division was abolished and distributed amongst the three remaining divisions. Cloak Lane Police Station was closed down in 1946, and D Division was transferred to the new Wood Street Police Station. The divisions after 1946 therefore stood at:

In 1984, the force was reduced to two territorial divisions, based at Snow Hill Police Station and Bishopsgate Police Station (still B and C Divisions), together with support divisions, and the divisions subsequently stood at:

In February 2009, all the divisions were abolished and the force was divided into directorates (with all patrol officers falling within the new Territorial Policing Directorate, subsequently incorporating certain specialist units and becoming the Uniformed Policing Directorate). All officers' collar numbers were then suffixed by the letters "CP" rather than a divisional letter. In a fashion similar to the Metropolitan police,some units such as Traffic and the Support Group, have their collar number supplemented by either the T or U respectively in order to differentiate their additional training and skill set.

Collar numbers are allocated as follows:

Metropolitan Police

A number, followed by one or two letters indicating the station/sector, borough, or unit. Current practice favours use of borough codes rather than station codes (with the borough code generally taken from one of the borough's stations—see below—which can cause confusion).

Divisional area codes are still used to identify the areas themselves, together with the police station and vehicles (if any) nominally covering them, but not officers.

A one, two or three digit number denotes a Sergeant, a three or four digit number denotes a Constable, a four digit number beginning with 5 denotes an officer of the Metropolitan Special Constabulary, unless they're attached to a 'Roads & Transport Policing Command' (RTPC) team, in which case the number will begin with an 8 and a four digit number beginning with 7 denotes a PCSO again unless they are attached to RTPC and they will start with a 6. Confusingly, MPS epaulettes display the letters over the digits, i.e. 81FH (a Sergeant based at Hammersmith) would show FH over 81 on their shoulder, which reads more like FH81 (the call sign of a panda car based there). Ranks above Sergeant do not have collar numbers – officers are identified by name (e.g. Inspector Smith, who may once have been PC 123 kg Smith), or warrant number.

An exception to the above was the City of Westminster borough. Westminster had over 1,500 officers therefore a three digit number system was too small. Until late 2009 constables and sergeants had four digit shoulder numbers beginning 1, 2, 3 or 4 (with the leading number signifying which part of the borough you were attached to – 1 Westminster North, 2 Westminster Central, 3 Westminster South or 4 Westminster HQ). With the amalgamation of Westminster Central and South in late 2009 the decision was taken to amalgamate all the shoulder numbers into one numbering system. All new officers joining the borough were given the first available number and cross division moves no longer resulted in the need for a new shoulder number.

Sussex Police

All officers will be provided with a collar number which is also their warrant number. Prior to September 2018, this was deemed by gender for example CS123 would represent a male officer whose surname started with S, a female would being with a D, DS123 for example.

The second letter would be the first initial of the officer, followed by a three digit number. In September 2018, this changed and all new officers warrant numbers start EA followed by a three digit number. Following the full use of the EA numbers from 1–999, they now start EB.

PNC codes and collar numbers

When a police officer or a member of staff is in a collaborative (multi-constabulary) unit or department (such as the Bedfordshire, Cambridgeshire and Hertfordshire Road Policing Unit), the PNC code, which is a force identification number, is added to the collar number to prevent confusion between officers; e.g., 41-9999 would indicate a Hertfordshire officer. These numbers are only used in paperwork and are not seen on the officer's epaulettes.^[5]

HM Prison Service

Operational Support Staff and sworn Prison Officers in His Majesty's Prison Service bear collar numbers to aid in accountability in the service. Collar numbers bear two letters indicating which establishment the officer is based at and three random numerical digits.

In fiction

The collar number of George Dixon of Dixon of Dock Green was O 706.