The most widely adopted free and open-source engine to write rules as code

Government departments, lawmakers and civil society finally share a common language to debate and activate social and fiscal policies: OpenFisca enables collaboratively modelling laws and regulations and making them computable over open APIs for developers, datascientists and researchers.

Policy experts and governments

OpenFisca enables institutions to efficiently share regulation updates and to pool IT costs. Interconnecting rules across public bodies in the form of legible parameters and executable code provides algorithmic transparency and reduces the bill for the taxpayer.

Developers and datascientists

OpenFisca enables developers to easily deliver apps calculating complex taxes and benefits through its JSON web API, and datascientists to compute large-scale through its vectorial Python API. Contributing formulas and coding extensions enables building services for any business.

Economists and researchers

OpenFisca enables economists and researchers to use survey and administrative data to simulate the impact of any past or future reform on the income distribution of a given population. Linking all computed taxes and benefits enables analysing how multiple reforms interact.

Some services built with OpenFisca

Get started with OpenFisca

Choose a country package

Define the jurisdiction in which you operate and access its rules model.

Run a simulation

Calculate values on situations you provide, of one person or of millions.

Improve the model

Collaborate with other contributors to model new laws, update legal values, handle edge cases, add tests, improve documentation… Country packages are open-source, so you're never alone!