The block 3XX corresponds to the seventh area of the ISBD bibliographic description. This block contains notes – free text statements qualifying and amplifying the description and access points and dealing with any aspect of the physical make-up of the item or its contents.

Certain types of notes may follow ISBD rules for content and form, including punctuation. Notes are in the language of the bibliographical agency. Standard preliminary phrases and abbreviations are used.

If a note belongs to more than one category represented by fields 301 to 318, then the tag earlier in numerical order other than 300 should be used as a general rule. Notes relating to fields 320 onwards should be entered in those specific fields and not in earlier fields. If two notes belong to the same category they should be contained in separate occurrences of the required field.

A note may be generated from data in other fields, e.g. 4XX linking fields. If such a note is to be generated, it is not entered in a 3XX field.