In the UK, the Fixed-term Parliaments Act 2011 sets the interval between general elections at five years. Each Parliament is usually divided into five parliamentary years called ‘sessions', beginning and ending in the spring. Note before 2010 the sessions generally ran from autumn to autumn.
House of Commons paper: HC Paper
House of Commons bill: Bill
House of Lords paper: HL Paper
House of Lords bill: HL Bill
Numbering for HC and HL papers and bills begins at ‘1’ at the beginning of each parliamentary session.
Command paper numbering runs from 1 to nearly 10, 000 across many parliamentary sessions. Command papers with the same numbering are differentiated by the letter prefix.
 to  1833-1868/69
C.1 to C.9550 1870-1899
Cd.1 to Cd.9239 1900-1918
Cmd.1 to Cmd.9889 1919-1955/56
Cmnd.1 to Cmnd.9927 1956/57-1985/86
Cm.1 to CM 9756 1986/87 -2018
CP 1, 2018-
For more information please see : 'About parliamentary papers' on the UK Parliament website
Cite the title, author, parliamentary session and paper number (as written on the document) according to your citation style. It may not be possible to work out the sessional year for command papers however the publication date should be sufficient.
When using the UK Parliamentary Papers database click on the details tab for bibliographic information.
'Antisemitism in the UK', House of Commons Home Affairs Committee, HC 136, 2016-17'
'The Bribery Act 2010: post-legislative scrutiny', House of Lords Select Committee on the Bribery Act 2010, HL Paper 303, 2017-19
'The Northern Ireland Protocol', Cabinet Office, CP346, 2020