Before you start

A French tax number, issued after your first declaration
Records of worldwide income for the year
A French bank RIB
Credentials for impots.gouv.fr

Step-by-step

1
Understand that withholding does not replace the declaration
Prélèvement à la source deducts tax from your salary, but the annual declaration in the spring is still mandatory. It reconciles what was withheld, applies the household quotient and reliefs, and captures income the withholding never saw. Missing your first declaration is a common and avoidable newcomer error.
OnlineWho: YouSpring annually
2
File your first declaration on paper if you have no tax number yet
The online service needs a tax number, which you do not have until you have filed once. The first declaration is therefore usually made on paper to your local tax office. This circularity catches everybody, and the tax office is used to it — ask them directly.
In personWho: You
3
Work out your parts and what the quotient does for you
A single person is one part, a married or PACSed couple two, with additional half-parts for children. Income is divided by the parts, taxed on the scale, and multiplied back. The effect is a substantial reduction for couples with unequal incomes and for families, and it is why French tax feels very different depending on your household.
OnlineWho: You
4
Establish your residence position for the year of arrival
France taxes residents on worldwide income. Your year of arrival is usually split, with foreign income before the move treated separately, but the rules and any treaty with your previous country matter. If you have significant income from both sides of the move, take advice on the first declaration.
In personWho: You
5
Declare foreign accounts — the penalty for not doing so is real
French tax residents must declare all foreign bank accounts, life insurance policies and digital asset accounts annually, on a dedicated form alongside the main declaration, whether or not they generated income. The fixed penalty per undeclared account is significant and it is applied.
OnlineWho: You
6
Know that you owe no residence tax on your home
Taxe d'habitation on main residences has been abolished. Owners still pay taxe foncière and second homes still attract the residence tax. As a tenant of your principal home, you owe the commune nothing — a genuine difference from the UK's Council Tax.
OnlineWho: You

Documents you’ll need

French tax number, once issued
Salary statements and the annual employer summary
Records of all foreign income and foreign accounts
RIB for refunds and payments
Marriage or PACS documentation, for household parts

Things most newcomers don’t know

France taxes the household, and that changes the answer completely depending on who you are.

The quotient familial divides household income by a number of parts — one for a single person, two for a married or PACSed couple, additional half-parts for children — before applying the scale. A couple with one high and one low income pays substantially less than two individuals earning the same amounts would. Conversely a single high earner does comparatively badly. Any comparison of French tax against a country with individual taxation is meaningless without specifying the household.

Source: impots.gouv.fr

You must still file, and the first one is usually on paper.

Withholding at source is not the end of the obligation, and the online service requires a tax number you only receive after filing once. So the first declaration typically has to be made on paper to the local tax office. Newcomers assume that since tax is being deducted there is nothing to do, and then find themselves reconstructing a missed declaration a year later.

Source: impots.gouv.fr

Undeclared foreign accounts carry a fixed penalty per account, per year.

French tax residents must list every foreign bank account, life insurance contract and digital asset account annually, regardless of whether it earned anything. The penalty is a fixed amount per undeclared account and it is applied rather than theoretical. A dormant account in your home country that you have not thought about in years is exactly the kind of thing that triggers it.

Source: impots.gouv.fr

No residence tax on your home is a real recurring saving against the UK.

A British tenant pays Council Tax to the local authority — several hundred pounds a month in many cities, on top of rent. A French tenant of their principal residence pays nothing equivalent, because taxe d'habitation on main homes was abolished. When comparing a Lyon package against a Manchester or Bristol one, this belongs in the calculation and it is routinely left out.

Source: service-public.fr

Common mistakes to avoid

Assuming withholding at source removes the obligation to file annually.
Being unable to file online in year one and not realising the first declaration goes on paper.
Failing to declare a dormant foreign bank account and incurring the fixed per-account penalty.
Comparing French and foreign tax rates without accounting for household quotient parts.
Overlooking that social contributions are separate from and additional to income tax.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.