A Vendor ID is a provider-created value that uniquely identifies one film from all other films delivered to iTunes. This identifier is used for tracking and reporting. Every film must have a unique Vendor ID. Vendor IDs may not be changed, reused, or duplicated.
The Vendor ID can only contain alphanumeric characters and underscores; it cannot contain spaces, dashes, ampersands, other punctuation, or symbols. The Vendor ID is case-sensitive and must not start with an underscore. As long as these specifications are followed, you are free to create any kind of Vendor ID up to 100 characters long. Some providers choose a Vendor ID based on their own internal system or for sales reporting. Many providers use the UPC or film’s title and release date, or a combination of both.
You cannot change a Vendor ID once it is created in the system. You can update other metadata on iTunes Connect, or you can ask your encoding house to deliver the updated metadata of assets to an existing Vendor ID.