Taxes (mainly VAT) should be handled properly. As pricing and tax data is almost never supplied by the buyer on incoming orders, you need to resolve the correct tax rate that applies to the specific document from the ERP system.
If the ERP system does not automatically apply correct tax rates when you import a transaction pulled from Procuros, you will need to determine the correct rate yourself the same way the ERP system does when users manually add orders into the system.
Each line item in an invoice must have a tax attribute provided in the payload. You will need to determine this tax rate, amount, and description from the ERP system.