During Vendor creation, the following validations are performed:
• Vendor name validation
It's checked whether there is already a QuickBooks Online Vendor with the same name on record. If this validation fails, an error pop-up will prompt you to change the Vendor name.
• Vendor duplication
If two users are creating a new Vendor with the same name, only the first user will be successful. The second user will receive an error message saying that a Vendor with this name already exists.