On the Launch page of the QuickBooks Export, there is a Create Customer Records option where you can choose whether or not you'd like QuickBooks to create Customer records when you import the data into QuickBooks:
Why is QuickBooks creating Customer records even when that option is set to 'No'?
On the QuickBooks Export screen there is an additional field called QuickBooks Transaction Type, which has options for Cash Sale and Deposit:
When the QuickBooks Transaction Type field is set to Cash Sale, the import in QuickBooks will always create a Customer record, even if the Create Customer Records field is set to 'No'. The type of transaction that is created in QuickBooks when Cash Sale is selected requires that a Customer record be set up for the donor.