The Charitable Incorporated Organisation – CIO – is a relatively new form of incorporated legal structure that is designed to meet the particular needs of a charity and is only available to charities. A CIO is a corporate body which is not a company incorporated under the Companies Acts; it is therefore not subject to company regulation. Neither its existence nor any charges it creates have to be registered at Companies House.
The corporate structure provided by the CIO meets a demand from the charitable sector for a structure which gives a charity a legal personality of its own, enabling it to conduct business in its own name, rather than in the names of its trustees.
More information can be found on the Government website: https://www.gov.uk/guidance/charity-types-how-to-choose-a-structure