We have a need to integrate to QuickBooks Online can you confirm you can read in the XML quote file and populate the line item details for a Sales Template or Estimate.

Hi there, paul-d.

Are you trying to import your products or services details using an XML file? QuickBooks Online only accepts CSV and Excel file formats when importing data. 

You might want to convert your file to Excel or CSV so you can import them in QBO. Let me also share this guide about importing for additional info: Import Products And Services From Excel.

Let me know if you need anything else.