The documents in this series are a major source for the records of the medieval council, the council in Parliament, and of Parliament itself.

They include conciliar agenda; memoranda of, and memorials presented to, the council; petitions in both original and copy, with answers and further proceedings on the same, including enrolments in the nature of Parliament rolls; lists of petitions; enrolments, drafts and copies of statutes; returns and lists of MPs; appointments of clerical proxies; and parliamentary bills and acts.

From the fifteenth century the records are primarily those of Parliament, but continue to include petitions to do justice presented to the council in Parliament, as well as original, draft and copy bills, acts and ordinances. There are also a few writs and returns, including summonses before the council, and returns on writs of certiorari, which are strays from the administrative and judicial writ files of Chancery.

Individual documents within the series relate not only to England and Wales but also to Ireland and the Channel Islands, to Scotland, to English possessions in France, including petitions from Gascony, and to the conduct of war and diplomacy.