The OpenFisca community gathers around a Slack space, which you can ask to join by sending a mail to

This space provides both community and official support, and centralises all countries’ channels.

Channels and naming conventions

In order to increase discoverability of channels and ease navigation, the following prefixes are used:

  • of- channels are about quick discussions and requests for help on a technical module. To make decisions on changes to apply to these modules, we use GitHub issues and Pull Requests on dedicated repositories.
  • share- channels are newsrooms on which everyone is encouraged to share their news, learnings and accomplishments  :)

For tax and benefit systems models, the following conventions are applied:

  • Channels that centralise discussions around a specific tax and benefit system are given the name of the distributed module, suffixed by -system. For example: france-system. If that full name is too long for the Slack channel character limit, then a shortened version of the name is used.
  • Channels that centralise discussions around extensions to tax and benefit systems are given that system’s module name, followed by -ext- and an identifier for that extension. For example: france-ext-paris.
  • System-specific group channels are campfires around which some specific organisations of contributors to a tax and benefits system gather. When a country becomes large enough, it often happens that several employers of contributors work concurrently on different parts of the system, and the main -system channel would become unreadable. These channels are called that system’s module name, followed by -org- and an identifier for that group. For example: france-org-gouv.


You can contact the OpenFisca maintainers through:

  • GitHub if you have any technical issue.
  • Twitter @OpenFisca for general inquiries and feedback.
  • email for collaboration opportunities.

Project history

The development of OpenFisca began in May 2011 at the CAS (renamed France Stratégie / Commissariat général à la stratégie et à la prospective in April 2013) with the support of the IDEP.

OpenFisca was originally developed as a desktop application using the Qt library with a Python API. This original source code was released under a free software license in November 2011.

In the early 2014, Etalab started using OpenFisca and soon became a major contributor. It then decided to:

  • separate the computing engine from its desktop user interface;
  • offer a web API in addition to the Python API;
  • demonstrate the value of the web API by developing sample applications including a web interface to simulate personal cases;
  • offer a public access to this web API;
  • stop the development of the Qt version.

The core was improved extensively by Etalab, while the French model was being improved and updated by the CGSP with the help of the IDEP and the IPP, soon to be joined by the French State Startups incubator which used and extended the model for digital public services purposes.

The 2016 OGP Paris summit saw a demonstration that a small team could model the base of a tax and benefit system from scratch under 36 hours, when the Sénégal income revenue tax was modelled and made usable with a web UI during the OGP hackathon, winning the team the first prize.

This led in 2017 to a joint effort from Etalab and with a major focus on stability, ease of contribution and reusability. This lead to the full rewrite of the documentation, the opening of to replace, and the addition of new contributors from other French agencies, as well as international reusers with Barcelona joining Tunisia.