A late fee automatically added by RepairShopr to invoices is treated as a non-inventory item and thus syncs over to QB using the Default QuickBooks Product defined in your QuickBooks settings (see https://yourdomain.repairshopr.com/quickbooks/settings or Admin > Apps > Quickbooks > Sync Settings).

If you want a specific late fee item to sync to QB, you will need to create your own Late Fee item in your Inventory and then manually add it to any late invoices.

If the late fee is non-taxable, then make sure the Default QB Tax code for non-tax items is set to a non-taxable QB code (found on the same settings page).

You will also need to make sure none of your Payment Terms include a late fee so that you can manually add your own.