OpenFisca is a free and open source calculation engine that enables the modelling of socio-fiscal systems in a collaborative and transparent manner. It allows users to compute a large number of social charges, social benefits and taxes, and to simulate the impact of reforms on these sums. Developed in France by Etalab and BetaGouv, OpenFisca is now used in 10 countries around the world.

OpenFisca is a community powered by Etalab and BetaGouv, two departments of the French Inter-ministerial Directorate for Digital Affairs (Direction interministérielle du numérique, DINUM). OpenFisca is a modular, reusable open source project. It allows users to model legislation into computer code, to improve transparency and to facilitate easier access to the law. Users can outline their tax and benefit systems, provide inputs (e.g. income) and ask for a calculation output.

 The target users for OpenFisca are mainly:

• Economists: OpenFisca allows users to input data to the software to simulate the impact of a reform on a given governmental budget and on a population’s standard of living.
• Developers: OpenFisca allows users to easily create web applications based on simulation results, thanks to the software’s web API. This feature allows users to develop websites based on OpenFisca with limited additional coding needs.
• Public administrations: OpenFisca prevents users from having to build expensive proprietary simulation software for tax and benefits calculation. Instead, the open source software provides a collaborative alternative to mutualise spending.

So far, ten countries’ socio-fiscal systems are available on OpenFisca. Additionally, developers can either use the country package template to set up the software for their own country’s legislation or contribute to an existing system by adding or improving elements. The customised solution can be deployed through the Web API to build an interface for online use, or for researchers through the Python API. OpenFisca’s source code is available on GitHub under an AGPL- 3.0 License.

In France, OpenFisca has enabled many digital public services such as mesdroitssociaux.gouv.fr, a simulator for French citizens to test their eligibility to over 32 social benefits and leximpact.an.fr, a tool to simulate the impact of tax reforms on governmental budgets and households’ purchasing power. Internationally, OpenFisca has been implemented in 10 countries such as Mali, Uruguay and Italy. Some of the use cases are Les meves ajudes, a web interface for Barcelonans to assess their eligibility for social benefits, Rapu Ture, a web interface to explore New Zealand's legislation, and a website for New South Wales allowing citizens, civil servants, policy officers and developers to find more information on government rules.

More information

OpenFisca GitHub Repository