<xs:simpleType name="InvoiceNumber" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:annotation>
    <xs:documentation xml:lang="de">Rechnungsnummer</xs:documentation>
    <xs:documentation xml:lang="en">Number of the invoice </xs:documentation>
  </xs:annotation>
  <xs:restriction base="DocumentNumber" />
</xs:simpleType>