Names are globally unique in QuickBooks.
When creating a Customer, if there’s any other entity (not just Customers) with that name, it will keep trying to create a customer by adding parenthesis and a number after it.
Example: John Smith (1), John Smith (2), until it finds a name not in use.
QuickBooks customer naming
How do we name a Customer when creating it in QuickBooks?
Written by Matt Honeycutt