An official government paper presented to Parliament, “by command of His/Her Majesty”, and given an official reference number.

The reference number follows a prefix (Cd, Cmnd, Cm etc) which has changed over the years since it was introduced in 1870.

1 to 4222 (1833 – 18690)

C 1 to 9550 (1870 – 1899)

Cd 1 to 9239 (1900 – 1918)

Cmd 1 to 9889 (1919 – 1956)

Cmnd 1 to 9927 (1956 – 1986)

Cm 1 to 9751 (1986 – 2018)

CP 1 to ? (from 2019)

Source: Public Information Online