XML Reports and Fields

Hi! I’m interested in understanding how we extract data from Dynamics Nav when downloading reports out of the box. I need to investigate this because there seem to be discrepancies between the data we pull from our data warehouse and the reports generated directly from Dynamics Nav. We have custom fields with similar names, and it’s important to identify which fields are being utilized in the standard report generation process within the ERP. Can someone please tell me how or where I can see the field ID in a report so I can identify which fields we are using when generating reports? Thank you!