The XRechnung extension is especially relevant for the construction industry, but other industries can benefit from it as well.

Although the XRechnung standard already makes it possible to submit invoice types which are specific to the construction industry (interim invoices, partial invoices, final invoices), the XRechnung extension covers additional industry-specific requirements. For example, the XRechnung extension makes it possible to embed XML attachments and thus add GAEB files[1] to your invoice as supporting documents. In addition, invoice lines can be structured so that the sub invoice lines can be used to show specifications. 

[1] GAEB files are based on a uniform standard agreed on for exchanging information in the construction industry. This standard expands, harmonises and improves all the requirements for electronic processes with regard to construction work (