For each patent in DWPITM, the patentee is assigned a 4-letter code. All patentees carried on the original source document are assigned codes, and the code is normally based on the name of the patentee. The Patent Assignee Codes formats are:
| DWPI on STN | DWPI on Derwent Innovation; DWPI on Dialog | DWPI Abstract Products | |
| Standard | ABCD; ABCD-C | ABCD | ABCD |
| Non-Standard | ABCD-N | ABCD-N | ABCD- |
| Individual | ABCD-I | ABCD-I | ABCD/ |
| Russian/Soviet | ABCD-R | ABCD-R | ABCD= |
Approximately 21,000 companies which have more than 500 patents in DWPI are regarded as ‘standard’ companies and assigned a unique four-letter code. These standard codes encompass known subsidiaries as well as the parent company, and so provide a valuable search tool for obtaining a complete set of DWPI records relating to an organisation as a whole. To find the standard patent assignee code for a company, use the Patent Assignee Codes Lookup Facility. Since 1970, ‘non-standard’ assignee codes have been assigned to companies and institutes that do not file a large number of patents. These codes are allocated using a set of simple rules and the list is growing continually. Non-standard company codes and Individual assignee codes are often not applied uniquely to a particular company/person, and so are of limited value for searching. In these cases a search of the assignee names will give a more precise retrieval.
For further details on assignment of PACO, see the document below.
Assignment of standard PACO
The DWPI Patent Assignee Codes are revised regularly to incorporate new companies having 500 or more patents in DWPI, or to revise existing codes to e.g. add a new subsidiary.