Ask for the scope certificate number + the transaction certificate for YOUR lot.
Check the number with the issuing body (Control Union, Ecocert, etc.) — name, address and product scope must match the seller.
Cross-match quantities: TC volume must cover your order. Over-selling one TC across buyers is the classic fake.
Tiaanz does this per shipment and files TCs by PO — ask us for a redacted sample pack with your quote.