1. Who must complete an income tax declaration form?

All members of the personnel (irrespective of the category of personnel to which they belong, employed or associated) who are French residents must complete a declaration form. Consequently, members of the personnel must themselves determine whether or not they are “domiciled in France” by referring to the criteria laid down by the the French tax authorities, namely:

• if their primary residence is in France (in particular if their spouses/partners and/or children reside with them); or
• if they perform their professional activities in France, whether in receipt of a salary or not, unless they can prove that the activity performed in France is a secondary; or
• if their economic interests are centred in France.

However, only the French tax authorities can assess individual circumstances. In the event of a specific issue or doubt, members of the personnel should contact the local SIP.

2. When to make an income tax declaration ?

Income tax declarations can be made online from 10 April 2025.

The deadlines for submitting the online declaration are:

• 22 May 2025 for departments 01 to 19,
• 28 May 2025 for departments 20 to 54,
• 5 June 2025 for departments 55 to 976.

The deadline for submitting hard-copy declarations is 20 May 2025, based on the date of the postmark (including for non-residents in France who are required to make a declaration).

3. How to complete the declaration form

3.1 Members of the personnel declaring their income in France for the first time (first-time declarants)

Members of the personnel who are filing their first income tax return in France are not yet registered with the French tax authorities. Their declaration must cover income received since their arrival on French territory during the reference year.

These individuals are required to take the necessary steps to file their tax return on their own initiative, and, except in specific cases, must do so using the paper format only.

To this end, they must complete at least the following forms and send them, along with supporting documents, to the Service des impôts des particuliers corresponding to their place of residence:

• Form no. 2042 – “Income Tax Return”;
• Form no. 3916-3916 bis to declare any bank account(s) held outside France.

Blank versions of these forms can be downloaded from the website www.impots.gouv.fr (enter the form number in the search bar), or obtained from a local office of the Direction Départementale des Finances Publiques (DDFIP): either from the Valserhône Service des impôts des particuliers (SIP) or its local branch in Gex.

The following supporting documents must be enclosed with the declaration:

• a copy of a valid identity document (e.g. identity card, passport, family record book, etc.);
• a copy of the rental agreement for their residence or another proof of address;
• a bank account identification statement (RIB);
• the internal tax annualcertificate and/or the individual annual statement.

After submitting their first income tax return in paper format (together with the required supporting documents), the person will be assigned a tax identification number (NIF). Upon receipt of the tax notice (see section 6 below), they will be provided with all the access codes necessary to create their personal online account.

Special case: Members of the personnel receiving a cost-of-living allowance — insofar as this income is taxable in France — may obtain a NIF upon arrival by completing a form 2043 and sending it, along with supporting documents, to the SIP corresponding to their place of residence (see question 1.8 of the FAQ prepared by the Valserhône SIP).

3.2 Members of the personnel with a tax identification number in France

Online filing is mandatory for everyone.

Members of the personnel who already have a tax identification number (NIF) in France must have created a personal account ("espace particulier") on the website https://www.impots.gouv.fr/accueil.

They will be notified of the opening of the online tax declaration service via the email address they provided in their personal account and will then be able to file their tax return as soon as the service becomes available.

Only members of the personnel who are technically or otherwise unable to file online may continue to submit a paper tax return. These members of the personnel will receive the necessary paper forms for the tax declaration in staggered mailings starting mid-April and continuing until the end of April. Otherwise, the forms can be downloaded from the website of the French Ministry for the Economy and Finance (type the number of the form you need in the search box) or obtained from the Service des impôts des particuliers (SIP) corresponding to their place of residence.

4. How to declare income received from CERN

N.B. A member of the personnel who has received both an internal tax annual certificate and an individual annual statement for the same fiscal year must follow procedures 4.1 and 4.2 respectively for the corresponding types of income.

See Question 1.9 of the FAQ prepared by the SIP of Valserhône.

4.1 Members of the personnel receiving an internal tax annual certificate

Each year, the Organization levies an internal tax (calculated according to the CERN scale) on the financial and family benefits that it pays to the members of the personnel. These members of the personnel receive an internal tax annual certificate from the CERN administration and are therefore exempt from national taxation on financial and family benefits paid by CERN.

In all cases:

1. Under the heading “Traitements, Salaires”, they must not indicate the amount of the financial and family benefits paid by CERN, which are subject to internal taxation by the Organization.
2. They must tick boxes 8FV and 8UU (if they hold one or more bank accounts outside France). These boxes are located in section 8, "Divers", of the hard-copy form. On the online declaration, this part can be accessed in step 3, "Revenus et charges" under the heading "Divers", by ticking the box entitled "Comptes à l'étranger, revenus de source étrangère, reprise de réductions ou de crédit d'impôt".
3. They must include the following statement at the end of the online tax declaration, under the “Informations – Mention expresse” section by ticking the corresponding box: “Membre du personnel du CERN assujetti à l'impôt interne du CERN et, à ce titre, exonéré d'impôt sur les prestations financières et familiales versées par le CERN” (Member of the CERN personnel subject to internal CERN taxation and therefore exempt from taxation on the financial and family benefits paid by CERN). If they submit a hard-copy form, the note must be added on page 2 under the heading "Informations" or on a separate sheet if this section is already pre-filled.
4. The internal tax annual certificate should be sent :

• either via the secure messaging platform available in the "espace particulier" on www.impots.gouv.fr,
• or failing that, by post to the local Service des impôts des particuliers (SIP) along with the reference number of the online declaration,
• or with the hard-copy declaration.

The internal tax annual certificate cannot be submitted by e-mail.

Members of the personnel are invited to consult the FAQ prepared by the Valserhône Service des impôts des particuliers, which answers the most frequently asked questions by CERN members of the personnel.

4.2 Members of the personnel receiving an individual annual statement

Members of the personnel who have received an individual annual statement from the CERN administration must complete their French tax declaration form as follows:

1. Under the heading "Traitements, salaires - salaires de source étrangère avec crédit d'impôt égal à l'impôt français" (box 1AF) and the heading "Revenus de source étrangère ouvrant droit à un crédit d'impôt égal à l'impôt français" (box 8TK): report the amount of salary and other income that is likely to be subject to tax in the home country; this includes cost-of-living allowance (COLA) if it is subject to tax in the home country;
2. Under the heading "autres salaires imposables de source étrangère" (box 1AG): report the amount of salary and other income that is not likely to be subject to tax in the home country; this includes cost-of-living allowance if it is not subject to tax in the home country; deduct from those amounts the premium paid for a compulsory health insurance scheme.
3. If the cost-of-living allowance (COLA) received through CERN is reported under 1AG (and is therefore taxable in France), actual professional expenses should be reported under the heading "Frais réels" (box 1AK). These costs will be deducted from the taxable income if considered by the French authorities as justified and linked to the professional activity of an associated member of the personnel sent by the employer to work at CERN. The deduction is applied at the taxpayer’s discretion: either a flat rate of 10% (applied by the taxes authorities) or actual expenses. These costs may include expenses for travel between the place of residence and the place of work, additional meal expenses, contributions to trade unions and insurance premiums for professional liability, professional training expenses, and costs associated with dual residency situation (rent, residence tax, water/electricity bills, and any other expenses incurred by the member of the personnel's presence in the region for professional activities, provided that the member of the personnel's need to reside in a different location than the partner/spouse's usual place of residence has been justified). A detailed calculation of these expenses should be attached to the declaration either on an individual sheet of paper or in the dedicated section of the online declaration. The actual receipts and bills must be kept by the member of the personnel for several years as they may be required by the tax authorities later for verification.
4. The individual annual statement should be sent:

• via the secure messaging platform available in the "espace particulier" on www.impots.gouv.fr,
• or, failing that, by post to the local Service des impôts des particuliers (SIP) along with the reference number of the online declaration,
• or with the hard-copy declaration.

The individual annual statement cannot be submitted by e-mail.

N.B. Members of the personnel who receive an individual annual statement must not tick box 8FV.

In the event of a specific issue, members of the personnel should contact their local SIP.

4.3 Associated members of the personnel receiving neither financial and family benefits paid by CERN nor a cost-of-living allowance

Associated members of the personnel receiving neither financial and family benefits paid by CERN nor a cost-of-living allowance may be liable for tax in France on other sources of income (e.g. remuneration paid by their home institute). Such income must therefore be declared to the local SIP, even if it is taxable in the country of origin of the payment.

Income (for example, remuneration paid by a home institute) is usually subject to tax in the country of origin. In some cases, a double taxation agreement exists between France, as the country of residence, and the country of origin, in which case it is taxed either in France or in the country of origin. In all cases, associated members of the personnel must use Form 2047 to declare income received from abroad.

N.B. This is not Form 2047–Switzerland, which applies to cross-border workers - a status that does not apply to members of the personnel of CERN.

1. If they receive from an institute outside France remuneration that is already taxed abroad, members of the personnel must enter at the end of the online declaration under the section "Informations – Mention expresse" the note “Membre du personnel du CERN (utilisateur/associé [as appropriate]), de nationalité … [their nationality], rémunéré par … [paid by: name and address of their employer], imposable en … [taxable in: the country where they are liable for income tax]”. If they complete a hard-copy of the declaration form, the same note must be added on page 2 under the section “Informations” or on a separate sheet of paper if that section is already pre-filled.
2. This foreign-source income (outside France) must be declared under sections 1 and 6 of Form 2047. In addition, only if the income is already taxed in the country of origin, the annual net amount before deduction of foreign tax must be reported in boxes 1AF and 8TK on Form 2042.

N.B. Associated members of the personnel are strongly encouraged to consult the relevant tax treaty between the Government of the French Republic and the country of origin, with a view to avoiding double taxation.

International tax treaties are available on the website impots.gouv.fr.

Members of the personnel concerned are invited to contact their local SIP regarding any specific issues relating to their declaration obligations.

4.4 Other income

For specific questions about how complete the various sections of the form in order to take into account any other income and individual circumstances, members of the personnel are invited to refer to the notes sent out with the tax declaration form (or available from the Ministry of Economy and Finance’s tax administration website) or to contact their local SIP directly. Useful information is also available in the FAQ prepared by the Valserhône SIP.

4.5 Foreign bank accounts

Foreign bank accounts (i.e. located outside France), including those into which any financial or family benefits are paid, must be declared. This declaration must be resubmitted every year (see point 4 of the document prepared by the Valserhône SIP).

Associated members of the personnel receiving other income should also refer to section 4.3.

5. Special cases

5.1 Members of the personnel of Swiss nationality resident in France

Swiss members of the personnel who are resident in France must complete the income tax declaration in accordance with the above instructions.

Those retaining a financial link with Switzerland (e.g if they own property in a canton) must also complete and return the Swiss income tax declaration form as described in the Income tax declaration in Switzerland procedure.

5.2 US citizens and Green Card holders

CERN is not able to provide advice on these very specific situations and invites the members of the personnel concerned to contact their local SIP and/or the US consular authorities. They may also refer to the FAQ prepared by the Valserhône SIP.

5.3 Former members of the personnel

• Retirees or other beneficiaries of benefits from the CERN Pension Fund

Benefits paid by the CERN Pension Fund are subject to standard taxation rules. Therefore, the procedure described below does not apply to such income (retirement pensions, disability pensions, or other benefits).

• Former staff members receiving unemployment benefits from CERN

Unemployment benefits paid to former staff members by CERN are also subject to standard taxation rules. As such, the procedure described below does not apply to this type of income.

6. Tax assessment notice

Members of the personnel who opt for an online declaration will receive an e-mail at the address indicated in their "espace particulier" as soon as their tax assessment notice is available. They will be able to consult it and, if necessary, download and print it.

Members of the personnel who have completed a hard-copy declaration and who are domiciled in France will receive by post, following their declaration, a document entitled “Avis d’impôt – Impôt sur les revenus”. This document must not be returned to the SIP. Members of the personnel must keep it.

The French authorities may request this document as evidence of their tax situation in France. Further information may be obtained directly from the local SIP.

7. Property and residence taxes in France

The Organization is not authorised to provide information on these types of tax. Members of the personnel are invited to contact a tax adviser ("fiduciaire") or the relevant national tax authorities for more information.

Further information is available on the website www.impots.gouv.fr and in the FAQ prepared by the Valserhône SIP (see point 3.3).

Since 2023, households are not subject to residence tax ("taxe d'habitation") for their primary residence, which is determined according to the address indicated on their income declaration (address on 1 January of the tax year concerned).

Residence tax still applies to secondary residences and vacant properties (see CERN Bulletin article). All owners of a primary or secondary residence or rented accommodation located in France must make an additional declaration to the French tax authorities on the website www.impots.gouv.fr. For more information, see the page "Real estate declaration".