If the Timesheet data is already transferred to Quick Books, then it will not affect billing information in Quick Books when the invoices are generated, because whenever there is change in billing information timesheet needs to reopened and saved.

Scenario1:
If the timesheet is submitted by user and then if the Project billing status is changed from Billable to Non Billable, this will not affect the data in Quick Books during the transfer, because timesheet is submitted before the change.

Scenario2:
If the Project Billing status is changed from Billable to Non Billable and then if the user submits the timesheet, it will make a difference in Quick Books billing information, because the timesheet is submitted after billing information is changed in Web Timesheet.

Note: Any timesheet submitted after the change in Project Billing Status and then transferring to Quick Books will affect the billing information in Quick Books.