You create and confirm three purchase orders to the same supplier (PO0001, PO0002, and PO0003).

The merchandise of the three purchase orders described above was independently received completely and successfully in the warehouse.

Each purchase order in its product lines has the requested and received quantities equal. The supplier has not yet sent the corresponding invoices. Then, instead of sending 3 invoices (one for each PO), the supplier sends a single invoice that includes the sum of the PO0001, PO0002, and PO0003 purchase orders.

This happens very frequently because it is export merchandise and the suppliers consolidate all the orders in a single invoice to save customs expenses.

How do I relate a single invoice in odoo with the 3 purchase orders already received previously?

When creating an invoice from the purchase order, the system automatically generates a supplier invoice for each purchase order, and in reality, it would be false to think that I have 3 invoices to pay, since the supplier only sent one invoice that adds the three purchase orders.