The type is cm:content (what are your invoice document types ?) and neither custom aspects are applied, so this is the expected behaviour. You should check your custom invoice model, and assign the corresponding types or aspects for these properties:
You need to know your custom model, you can inspect your content models using this tip:
If existing invoice data in your repo, you can also check the applied types and aspects via Node Browser tool (In alfresco repository administration console or even in alfresco share administration console).
I found in manual, that for bulk import, type can be folder (for folder) or cm:content (for file)
in my example I used <entry key="type">cm:content</entry> as a representation of file
I need to define special metadata, so I used <entry key="cm:type">Invoice</entry> to define metadata of custom type - Invoice.
next I tried to add custom metadata
<entry key="Invoice:Contractor">ABC</entry> etc
My model is working - it is correctly set, is active and has defined default layout, so I can add new Invoice manualy into repository.
My source repository has nodes as records in folders structure, record is defined by type which is defined by set of metadata, and for each record there can be assigned attachment (0:n). So it is possible that no real file is stored, only metadata. Metadata and attachment are versionable.
So my idea was to create folder structure as in source repo, and nodes as representative of my nodes. node should be defined by node_name.metadata.properties.xml and empty file node_name. When I prepare my source structures and run import, folder structure is created fine, nodes are created in place, but without type metadata. Another problem is with attachment so far.