openfisca-france

People might not know that, since it’s mostly in French, but France has somthing similar as open source for their tax system: https://github.com/openfisca/openfisca-france/

France has also developed the OpenFisca framework [1] for tax and benefit rules as code, and its OpenFisca France [2] model is widely used (I think significantly more than mlang). We've extended it to the UK [3] and the US [4]. [1] https://openfisca.org [2] https://github.com/openfisca/openfisca-france [3] https://github.com/policyengine/openfisca-uk [4] https://github.com/policyengine/openfisca-us

The french initiative started in 2013 is still alive (last commit a few days ago), and passes the gov test suite (they keep in touch with our version of the IRS): https://github.com/openfisca/openfisca-france The way we got this is interestingly twisted. French citizens requested the software used by the administration, and they managed to get it! But, it was written in Mlang, a proprietary language created by the french administration in the 90: https://github.com/MLanguage/mlang. Someone then decided to create an OCaml compiler that takes mlang and emits python: https://arxiv.org/abs/2011.07966 As a result, we got Open Fisca. I now think there are other techs in the mix... A slide of the story: https://www.slideshare.net/Etalab/opening-up-the-french-tax-... But I believe it should be mandatory for the state to provide the source of ever

That line in the summary is a bit misleading. The authors didn't find a "bug" in any law - instead they found a corner case that wasn't coverred by an online tool hosted by the French government to estimate family benefits under French law: > After close inspection of the OpenFisca code, a discrepancy was located with the Catala implementation. Indeed, according to article L755-12 of the Social Security Code, the income cap for the family benefits does not apply in overseas territories with single-child families. This subtlety was not taken into account by OpenFisca, and was fixed after its disclosure by the authors. Here's the pull request for their fix to the benefits simulator: https://github.com/openfisca/openfisca-france/issues/1426

You might be interested in the French example, if you don’t know already. They designed the Mlang DSL for tax calculation, and released a bunch of things on GitHub. Here is the compiler: https://hal.inria.fr/hal-03002266v3/document https://github.com/MLanguage/mlang They’ve also open sourced an official calculator, along with web APIs: https://github.com/openfisca/openfisca-france

The French government and parliament also use this implementation of the law (taxes, benefits, ...) : https://github.com/openfisca/openfisca-france It's open source and contributive so, a common structure is used by multiple countries. They are listed here : https://openfisca.org/en/countries/

Most of the French socio-fiscal system can be simulated in Python through https://github.com/openfisca/openfisca-france/.

There's a much broader project that can compute most taxes and benefits for France (and a few other countries) : https://github.com/openfisca/openfisca-france It would be quite interesting to check that both the French IRS implementation of the tax & benefit laws and the free software community (though most devs of the project were employed by the French admnistration) implementation of the tax and benefit laws actually output the same results.