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A Modern Compiler for the French Tax Code (2020)

189 points| sebg | 3 years ago |arxiv.org | reply

49 comments

order
[+] nayuki|3 years ago|reply
I wish the state officially makes their income tax calculation available as machine-executable open-source software in an industry-standard language. For example, a Python function that takes a dictionary of inputs (gross income, number of dependents, capital gains, etc.) and produces a dictionary of outputs (federal tax, state tax, rebates, contribution limits, etc.).

This would solve many problems: The verbosity and ambiguity of human language (tax laws, tax calculation forms in English), the ability to inspect and independently verify calculations done by the state, the rent-seeking tax preparation software companies.

Here is my own feeble demonstration of the idea: https://www.nayuki.io/page/a-math-programming-view-of-canada...

Even if the state has its own online portal for you to review and adjust your tax return, I still want to see the full tax code be open source and runnable by the user.

[+] masklinn|3 years ago|reply
> This would solve many problems: The verbosity and ambiguity of human language (tax laws, tax calculation forms in English)

1. It would not, the tax law remains the spec.

2. France does provide an executable encoding of the tax code, TFA is literally a compiler for that.

3. France started to do so circa 2016 (https://joinup.ec.europa.eu/collection/egovernment/document/...) after losing a FOIA-type case, though feelers had already been sent as a governmental agency (CAS) is at the root of OpenFisca (https://openfisca.org/), and by then the prime minister's data sharing and coordination office (etalab) had started using and contributing to it (https://openfisca.org/doc/manifest-history.html)

4. You can use OpenFisca to encode your own country's tax law, or lobby for your country to encode its tax law there (https://openfisca.org/en/packages/).

[+] andylynch|3 years ago|reply
While this could help with the mechanical calculations and preparation of returns, the wider point about ‘verbosity and ambiguity of human language’ can’t be nearly so easily dealt with outside the simplest cases, and would likely make the tax code /harder/ for people concerned to interpret and reason about, which is probably the opposite of the desired result.

Firstly the actual text of the law must be as legislated.

Secondly, law and most certainly tax law is necessarily nuanced in interpretation and the consequences for taxpayers and the government are material (to use a relatively simple and well-known British case, a machine-executable model would be unhelpful in determining whether Jaffa Cakes should be taxed for VAT as biscuits, or exempt as cakes. Then ask about chocolate chip cookies (zero rated) vs chocolate digestives (taxed!)). Stuff like this and more is argued about all the time.

[+] addcommitpush|3 years ago|reply
The French "income tax" (which, confusingly, is only one of the several taxes on income in France, and not the largest) is open source (https://gitlab.adullact.net/dgfip/ir-calcul).

There's also the OpenFisca project (https://openfisca.org/en/) which is a Python framework for coding tax and benefit system - France being the most complete - which is used in many things, like a web app to see which benefits you might be eligible to (https://www.mesdroitssociaux.gouv.fr/accueil/) or the French National Assembly tool to compute the effects of changing tax law (https://socio-fiscal.leximpact.an.fr/).

[+] nicbou|3 years ago|reply
Germany kind of does.

They publish all the diagrams for income tax calculation, if you can decipher them. It takes a while but you get it right eventually.

This is how I built my income tax calculator and keep it updated.

[+] krackers|3 years ago|reply
It would also allow people to re-use ML optimizers to get the highest tax returns!
[+] el_nahual|3 years ago|reply
I would accept just the test suite! For a given set of inputs here is your tax owed.
[+] LinkLink|3 years ago|reply
The year is 2030, after developing unrest the world government has decided the best way to subdue the population is to make taxes even more complicated. Entire family units are formed around starting on the years taxes 13 months before the next tax season, any attempt to simplify tax is killed by the turbotax lobbyists, who boast a legendary 11 month taxes turnaround. Paper supply is at an all time low due to economic returns, and most crime is centered around illegal paper trade in order to file a paper return, and avoid the automatic audit on any virtual returns submitted.
[+] maelito|3 years ago|reply
Another huge French "tax" set is the social contributions, that makes our payrolls quite complex.

Computing payrolls is handled by the private sector, contrary to the case of the income tax.

But the French administration develops an open source set of online simulators :

https://mon-entreprise.fr

This is the source code of the underlying "tax" rules :

https://github.com/betagouv/mon-entreprise/tree/master/model...

Is uses an open source specific language that frames the writing of simple calculation rules, auto-generates an online documentation for non-developers and helps developers build automatic UIs.

It is unfortunately not yet translated for English speakers and developers.

https://publi.codes

[+] Dowwie|3 years ago|reply
The old implementation didn't age well, but a newly invented language that 2 people understand will age much better.
[+] ape4|3 years ago|reply
Wow the old version is only 92K lines of M code.
[+] parentheses|3 years ago|reply
> which unlike French wine, did not age well with time. :chefkiss:
[+] gnad_sucks|3 years ago|reply
Is the logic for such calculations known for the US? What about the UK?
[+] thechao|3 years ago|reply
Given that you know to apply a specific tax rule, the logic is formalized for the US. The problem is knowing when a specific tax rule applies to a given tax situation. In general, the IRS has an opinion — and not matching their opinion can land you in an audit — but the nuts-and-bolts application is still an interpretation. The IRS is, in my experience, pretty flexible with their interpretation. While individual auditors can have their hands tied with respect to fines/fee-schedules, I've always found them easy to work with, and knowledgeable. The last time I was audited, I ended up starting with a $220 fine; however, the auditor requested I review the previous several years of returns (for the same class of error), and I ended up getting a substantial check.
[+] guerby|3 years ago|reply
From the article:

Unlike, say, the United States, the French system relies heavily on automation. During tax season, French taxpayers log in to the online tax portal, which is managed by the state. There, taxpayers are presented with online forms, generally pre-filled. If applicable, taxpayers can adjust the forms, e.g. by entering extra deductions or credits. Once the taxpayer is satisfied with the contents of the online form, they send in their return. Behind the scenes, the IR algorithm is run, and taking as input the contents of the forms, returns the final amount of tax owed. The taxpayer is then presented with the result at tax-collection time.

[+] phh|3 years ago|reply
Nowadays, some people (like if they just have French salaries and no tax breaks) can even not look at it at all and their automatic filling will be automatically accepted
[+] tmnvdb|3 years ago|reply
Same thing in the Netherlands, if you're a regularly employed person you usually just click 'next' a few times.
[+] secondcoming|3 years ago|reply
The system is the same in the UK, for people who have to do Self-Assessment.
[+] baud147258|3 years ago|reply
too bad the website is just a copy of the old paper forms in HTML form... Well at least I prefer using the website that to actually filling a paper form! (and being online make it easier to submit corrections if needed)