Can I import a second list of customers to add to existing without overriding existing list?

Yes, Michael, it is possible to import several customer lists into QuickBooks Online without affecting the current list.

Importing an additional list may lead to duplicate entries if there are customers with identical names. It is essential to ensure that each entry is unique. You can modify or include extra characters in entries that share the same name.

This article offers valuable insights on key considerations to review before importing files into QuickBooks: Import customers or vendors from email contacts to QuickBooks Online.

To obtain a printed customer register, refer to this article for detailed instructions: Print a customer or vendor register in QuickBooks Online.

If you have any further concerns about the import process or need guidance on how to navigate through QuickBooks Online, drop a comment below. I'd be delighted to help you out.