DHL use the labels Non-Doc and Doc to identify the type of consignment.
Doc (non-dutiable)
These are consignments with no monetary value and are known as documents or general correspondence.
Non-Doc (dutiable)
All other consignments classified as dutiable by Customs may be levied customs duties and taxes for entrance into the destination country.
Note on Domestic Consignments: Domestic shipments are considered Non-dutiable or Doc.