Company Mergers and Demergers
If two organizations (with standard DWPI Patent Assignee Codes) merge, the standard policy is to continue to apply the standard Patent Assignee Code for each organization as long as patents filed under the names of the independent organizations continue to appear.
For example, following the merger of Sandoz (SANO) and Ciba (CIBA) to form Novartis, the SANO and CIBA codes continued to be applied to those patents filed under the names of Sandoz and Ciba. Ongoing filings made under the Novartis name receive a new standard code 'NOVS'.
Note that Thomson Reuters does not automatically assign a new standard Patent Assignee Code when two large companies merge or are involved in takeovers/demergers etc. Each case is assessed individually and the most appropriate action taken. So in the case of Novartis (merger) and Zeneca (demerger from ICI) new codes were created, but with GlaxoSmithKline and Bristol-Myers Squibb, one existing code was retained and the other abandoned.
Patentee codes are not generally changed retrospectively to reflect mergers and demergers as Thomson Reuters does not track the assignment of patent rights from one organization to another.