Can I have duplicates of customers/vendors with the same display name?

Yes. The option to allow duplicates of customers/vendors with the same display name is enabled by default.

If you wish to disable it, kindly follow the instructions below:

• Click on the Gear icon present on the top-right corner.
• Go to Preferences section.
• Click on the Customers and Vendors tab and you will see the Allow duplicates for customer and vendor display name option.
  
• Uncheck the option and click Save.