Are you married or in a civil partnership? We explain why your withholding tax rate is changing, even without an increase in income.

Starting this Monday, September 1, 2025, the Directorate General of Public Finances is implementing a discreet but far-reaching reform for many households: without their income having changed, millions of married or civil partnership couples will see their withholding tax rate change.

The cause: the generalization of the individualized rate , now applied by default.

The end of the common default rate

Since the introduction of withholding tax in 2019, couples have been able to choose between two formulas: the common rate, calculated on the entire household income, and the individual rate, which distributes the tax according to the income specific to each spouse.

Until now, the first one was applied by default.

From today, it will be the opposite: the individual rate will be automatically imposed , unless the couple has expressly checked the box to keep the joint rate when filing their declaration. This switch should affect nearly 10 million households .

The stated objective: to correct a distortion which, in many cases, penalized the spouse with the lowest incomes.

Concretely, what is changing?

Let's take the example of a childless couple where one earns €1,600 and the other €3,500 per month. With a common rate of 5.8%, each was taxed at the same percentage : €93 for the first, €203 for the second.

Now, with the individualized rate, the distribution is adjusted : 0.4% for the first (€6 per month), 8.3% for the second (€290).

The overall tax amount remains the same, but the tax burden is spread more fairly between the two pay slips.

A symbolic reform

While the monthly gain may seem modest - sometimes a few dozen euros for those who earned the least - the scope of the reform goes beyond simple calculation.

It corrects a bias which, statistically, affected women more , whose average salary income remains more than 20% lower than that of men.

The Minister of Public Accounts had also presented this development as a lever for equality within couples: each now contributes in proportion to their income, without one person disproportionately bearing the tax burden of the household.

And for those who want to keep the common rate?

There is nothing to prevent you from going back to the old system.

Couples who prefer to share the tax evenly can indicate this in their personal space on the tax website , under "Manage my withholding tax".

The administration will then transmit the new rate to the employer, who will have two months to apply it.