Your prélèvement à la source rate changed in September — check it

In France income tax is withheld from your salary — this is prélèvement à la source. The rate is set by the tax authority from your most recent return, and it changes every year in September. So the percentage on your September payslip is often not the one from August, and that is not a payroll mistake.

Where the rate comes from

The rate is calculated for the whole tax household (foyer fiscal), not for one person. Two people on identical salaries can therefore have different rates: a spouse's income, children and deductions all feed into it.

For married and PACS couples the rules provide an individualised rate: each partner's own income — salary, pension, self-employment — is taxed at their own rate, while income held jointly uses the household rate. A couple may go back to a single shared rate by requesting it in their online account.

If you have not filed a return yet

If you have just arrived and have never filed, there is no personal rate yet. A neutral rate applies (taux par défaut), taken from a scale based on your monthly salary and running from 0% to 43%.

The neutral rate knows nothing about your family or your deductions, so for someone with children or on a modest income it is often too high. Overpaid tax is not lost — it comes back after your first return — but until then the money sits with the state rather than with you.

There is a deliberate flip side worth knowing: the neutral rate is also the way to avoid telling your employer your personal rate. The rules let you choose it on purpose if you would rather not have your household's finances inferred from a percentage.

How to change the rate

You can change the rate in your account on impots.gouv.fr: raising it is up to you, lowering it is possible under certain conditions. This is a case where acting is worthwhile: the rules provide for changes when circumstances change, and for people who have recently arrived such changes are frequent.

Common reasons:

• income has risen or fallen noticeably — a new job, a contract ending, a move to part-time;
• the household has changed — marriage, PACS, a child (the rules provide for reporting such a change to the tax office within 60 days);
• your first full year in France after arriving part-way through the previous one.

A change normally takes effect within three months — so a request made in October shows up towards the end of the year, not on the next payslip.

Why it is worth checking now

The September rate is calculated from the return filed in spring, that is, from last year's income. For someone who arrived in France recently, that often means a partial year: arrive in September and your return shows four months of income rather than twelve, so the rate comes out low. Withholding stays small all the following year, and the difference lands in one lump at the next calculation.

The reverse happens too: a year with a bonus or a severance payment pushes next year's rate up even though your income is back to normal.

You can see your current rate in your online account under "Prélèvement à la source", together with the rate that has actually been sent to your employer.