What types of documents do you need to verify an invoice?

The below documents:-

1. Valid Trade License or mention of License no on the invoice

2.DRF & Approved Quote with specification

3.Delivery Note with Recived Signature along with any warranty related documents

4.LPO issued

5.Inovice should carry the LPO no issued

6.Invoice should mention the description of the product and supplier quote reference no or agreement refernce no

It is important to start with breaking the Ice with any potential customer , open questions or talking about many points regarding things other that the subject concerned and elicit the needs and potential capacity to fulfill throughout such conversation.

procurement documents and material documents

It actually depends on what kind of items listed in the invoice.  If it is material delivery, the documents you needed are, Purchase Order, Bill of ladings, Delivery Notes, insurance and sometimes material origin.