Work order info gets attached to customer e-invoice

Hi,

When we create a customer e-invoice based on a customer order based on work orders,  information from all the underlying work orders are sent along the invoice as a separate attachment (named “invoice_specification”). This is a big problem for us as the work orders contain internal information that we don’t want the customers to see. We just want to send the invoice to the customers. 

How can we prevent the attachment with all the work order information to be created and attached to the customer e-invoice?

Thank you,
David