Search report

Patent law

Categories of documents

Letters are often included in search reports established for patent applications to indicate the relevance of the documents identified by the examiner. For instance, the European Patent Office (EPO) uses the following letters in search reports or in the European Patent Register:

Combinations of different categories are possible. For instance, a document classified as "D, A", i.e. in categories "D" and "A", would be a document cited in the application and regarded as representing the technological background of the invention.