You should update the sellers.json file when starting a new partnership with a seller or ending a partnership by adding or removing their details from the sellers.json file. Increasingly, Buyers won't buy traffic that is not verified by a sellers.json file. Including a new Seller in the sellers.json file ensures that all Buyers can access the traffic and the supply chain works appropriately. It is also recommended that you run quarterly maintenance to verify that active Sellers are included in the file, and obsolete Sellers have been removed.