DATEV enables all software vendors to implement Online APIs (DATEV Data Services) in order to be part of the Digital DATEV Ecosystem. Attached some information:
The documentation of the individual Online APIs can be found - without registration or login - under "Documentation" in the header navigation of the in the Developer Portal.
Information on the implementation process as well as the compilation of the APIs for the respective DATEV data service can be found at: How to integrate a DATEV Data Service
To integrate Online APIs for connecting DATEV Data Services you can register with the following form: Registration form
By the way: Via our new newsletter "Developer Portal - Newsletter for Software Developers" you can also be actively informed about new information concerning DATEV interfaces. You can set up the subscription via the following link: DATEV eG - Subscribe to Newsletter