Central Office of Information was established in 1946, as the Information Bureau, after the demise of the wartime Ministry of Information, when individual government departments resumed responsibility for information policy. The remit of the department was for the 'collection and recording of information on existing conditions in the Empire ... for the benefit of all who desire to avail themselves of this service.' The two principal and inter-related functions were: 'collection' which involves maintaining and housing the library's current reference materials ranging from substantial yearbooks to ephemeral pamphlets and press releases and 'recording' which involves publishing the papers in the Notes on Conditions series.

Both functions evolved over the years, mirroring the transition from Empire to Commonwealth and the varying needs of Notes readers. In the immediate post-war years, Notes were mostly used by people emigrating permanently from Britain. The later Notes are designed for expatriate employees who went overseas on contract jobs of up to about three years.

Whilst the Notes and related reference materials were the Bureau's main concern, the Information Officer also dealt with any Commonwealth current affairs enquiry received by the RCS. These ranged from advising schoolchildren and teachers on projects, to directing companies and other enquirers to sources of sophisticated information - including the RCS Library - on economics, markets and potential markets, and company-orientated and academic information generally. In addition, guidance on sources of expatriate information and literature on Commonwealth countries not covered in the Notes series (except Australia, Canada, New Zealand and the UK) was available, as was informal telephone briefing to Notes readers requiring supplementary information on specific points, and advice on expatriate recruitment bodies.

The COI had a substantial photographic library, used by the RCS on various occasions, particularly for illustrations to ‘United Empire, Commonwealth Journal’ and ‘Commonwealth in Focus’ in 1982. Numerous photographs are included in the ‘Modern commonwealth’ collection.

In July 1988 it was announced that the COI was dispersing this library and it was eventually divided among numerous libraries. The RCS applied to receive the Commonwealth material, and this was approved. It is understood that the material in the COI Library taken in Commonwealth countries was distributed among those countries years ago, though a few items of this nature remained in the material handed over in 1988.