You asked

Please provide details of how you obtain details of the number of police officer suicides and provide a copy of any specific forms used for this purpose.

We said

When a death is registered at a register office, the registrar records a number of details about the deceased which includes their occupation and cause of death. This is how the ONS can provide data on suicides by occupation. The cause of death is normally provided in a medical certificate of cause of death which is completed by the attending doctor. The occupation is supplied by the informant (usually a near relative of the deceased). Deaths that may have been a suicide should be referred to a coroner. In those cases the coroner will provide the information on cause of death and occupation to the registrar. The form used by the registrar can be found in Annex I of Mortality Metadata.

The medical certificate of cause of death can be found in Annex A and the coroner's certificate in Annex C.