When you click to issue the invoice DTE the software will ask if you want to add a purchase reference / HES, you must click on this option and then you must complete the fields:
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- Document type: you can select the options 801 - Purchase order, HES (service entry sheet), EM (goods receipt sheet)
- Folio reference: Mandatory field
- Date Reference: Required field
- Concept: Optional field, the information you indicate in this field is transferred to the XML.
Once you have completed the fields, you must make sure to click on Add +, next, the reference will be shown on the bottom left as added, you can add other references to the invoice, completing the fields again and clicking again on Add +, once you complete all the references you need you click on Accept and the DTE of the invoice will be issued.