Information notes are used in an authority record to provide historical information about an access point or to provide information when simple references generated from variant or related access points do not explain adequately a relationship. An information note in a reference record explains relationships between the reference access point and the authorized access point(s) to which the user of the reference is directed. Information notes in general explanatory records give the conventions used in formulating or filing authorized access points of the type one might expect to find under the form given in the explanatory access point.

Notes within the 3XX block are in textual form suitable for display to the public. Notes intended primarily to guide cataloguers are carried in the 8XX Source Information Block.