"The more children a household has, the lower its income tax rate" — France has had such a system in operation for 80 years, since 1945: the quotient familial (family-quotient system, known in Japan as "N-bun-N-jo" household taxation). For a household with income equivalent to 6 million yen, a rough calculation gives income tax of roughly 1.94 million yen for a single person, but only about 490,000 yen for a married couple with two children. In Japan, several political parties argued for introducing it in the Diet in 2023, but the government cited a number of issues and shelved the idea. This article walks through the mechanism, worked examples, the results of 80 years, and why Japan decided against it — based on primary sources (official information from the French government).
How it works: divide household income by the "number of family units" before applying the tax rate
Japan's income tax is levied on an individual basis — each spouse's income is taxed separately. France taxes on a household basis, calculated as follows.
- Add up the income of everyone in the household
- Divide the combined income by the "family quotient (N)". Each adult counts as 1; the first and second child count as 0.5 each; the third child onward counts as 1 each
- Apply the progressive tax rates to the divided amount
- Multiply the resulting tax by N again
Because progressive taxation applies lower rates to lower incomes, dividing first and then applying the rate means that larger families face lower tax rates. That is the heart of the quotient familial.
Example: income tax on household taxable income of 60,000 euros (about 10.5 million yen at 175 yen per euro)
- Single (N=1): about 11,100 euros (about 1.94 million yen)
- Married couple, no children (N=2): about 4,200 euros (about 740,000 yen)
- Couple + 2 children (N=3): about 2,800 euros (about 490,000 yen)
- Couple + 3 children (N=4): about 1,500 euros (about 260,000 yen)
* Calculated with the rate schedule applying to 2025 income (0% / 11% / 30% / 41% / 45%). Even with the same household income, the tax bill varies severalfold depending on family composition.
A cap for high-income households (the "plafonnement")
The tax reduction from children is capped: it can lower the tax by no more than 1,807 euros per year per child (per 0.5 quotient unit) for 2025 income. The system is designed so that wealthy families with many children do not benefit without limit.
Why it was created: a postwar policy to rebuild the population
The quotient familial was introduced in 1945, immediately after World War II. Having lost a large share of its population to the war, France made it a national goal that "having a family should not be a disadvantage under the tax system," and the quotient became one of the pillars of its family policy. It has been maintained for 80 years since, across changes of government, and together with generous family allowances and childcare programs it forms what is known as "French family policy."
80 years of results: a top birth rate in Europe, but not clearly "thanks to the quotient"
- France's total fertility rate long stayed at the highest levels in Europe (around 1.8 to 2.0) and was often called a success story of family policy. In recent years, however, it has been declining, most recently falling into the 1.6 range
- Among researchers, the prevailing view is that the birth rate was supported by the policy package as a whole, including extensive childcare and family allowances, and that it is difficult to isolate the effect of the quotient familial alone
- There is criticism within France as well. Two points are most often raised: (1) by the nature of progressive taxation, higher-income households receive larger tax reductions (there is a cap, but critics call it regressive), and (2) it favors single-earner households and discourages the second earner in dual-income couples (most often the woman) from working
Comparison with Japan: debated in the Diet in 2023 and shelved
In Japan, proposals to introduce a quotient-familial-style system have repeatedly surfaced in the context of measures against the falling birth rate. Most recently, in the Diet in January 2023, part of the Liberal Democratic Party, the Japan Innovation Party (Nippon Ishin no Kai), and the Democratic Party for the People argued for introducing it, and the Constitutional Democratic Party said it was "worth considering." The government, however, remained cautious and the idea was shelved. The issues cited were as follows.
| Issue | Details |
|---|---|
| Favors higher earners | The softening of progressive rates is largest for high-income households, and has almost no effect for low-income households (whose tax is small to begin with) |
| Can disadvantage dual-income couples | Combining household income can push up the tax rate on the second earner's income. Critics also called it "a tax increase on singles and dual-income households" |
| Different institutional foundations | Japan's system is built on individual taxation plus dependent deductions and child allowances. Switching to household taxation would be a major overhaul that rebuilds the withholding and year-end adjustment system from the ground up |
The goal — easing the burden on child-rearing households — is the same, but Japan chose the benefits route of expanding child allowances (the child and child-rearing support fund). How that program is financed sparked controversy under the label of a "de facto singles tax," as covered in the previous article in this series on Germany's childless surcharge. Where each political party proposes to support child-rearing within the tax system is summarized in our comparison of the parties' tax positions.
When it affects Japanese readers: household filing if you are posted to or living in France
- Japanese nationals working in France file, in principle, under this household taxation. Marriage, a PACS (civil solidarity pact), or the birth of a child changes your quotient and can move your tax bill substantially — so review your return in any year your family situation changes
- If one spouse stays in Japan (a "solo posting" arrangement), which country taxes what depends on the Japan–France tax treaty and residency determinations. It is safest to check with your company or a specialist before the posting
- If you are used to Japan's year-end adjustment, France's "everyone files" approach can be disorienting — but the standard method now is to review a pre-filled return online
What to do today
What to do today
- Run a rough calculation of "what my household's tax would be under the quotient familial" (divide taxable income by the family quotient and apply the income tax rate schedule — you will feel the difference from Japan's individual taxation)
- If you are raising children, check that you are not missing any of Japan's current benefits: dependent deductions, child allowances, and free high school tuition
- Compare the parties' positions on child-rearing and taxation (the quotient familial debate resurfaces at every election)
FAQ
Q. What is the "N" in the family-quotient system?
A. It is the family quotient. In France, each adult counts as 1, the first and second child count as 0.5 each, and the third child onward counts as 1 each. Household income is divided by N before the progressive rates are applied, and the tax is then multiplied back by N, so larger families face lower tax rates.
Q. Is France's high birth rate thanks to the quotient familial?
A. It cannot be attributed to the quotient alone. The prevailing view among researchers is that it is the result of the policy package as a whole, including extensive childcare and family allowances. Note that France's birth rate has been declining in recent years.
Q. Why did Japan decide against the family-quotient system?
A. Mainly three reasons: higher-income households would receive larger tax cuts; combining household income can work against dual-income couples; and it would require rebuilding the withholding and year-end adjustment system, which is premised on individual taxation, from the ground up.
Q. Does it amount to a tax increase for singles and childless households?
A. The quotient familial itself is a mechanism that lowers tax rates for larger families; it does not directly raise rates on single people. However, if overall rates are adjusted to maintain revenue, the relative burden on single and childless households grows — a point of contention both in France and in Japan's debate over introducing it.
References (sources)
* Rates and caps are those for 2025 income (filed in 2026). Yen conversions are approximate at 175 yen per euro. This article is provided for informational comparison of tax systems and does not advocate for or against any particular policy.