You need to declare the income you received in 2017 before May 17th 2018. Declaring your income does not mean you will necessarily have to pay the income tax.

You can download the declaration form on impots.gouv.fr or get it in your local tax office (service des impôts des particuliers, also called SIP).

After you filled in the form you will have to send it back to your local tax office or to the service des impôts des particuliers non-résidents if you left France.

Address: Service des impôts des particuliers non-résidents 10, rue du Centre TSA 10010 93465 NOISY-LE-GRAND Cedex Tel: 01 57 33 83 00 Email: sip.nonresidents@dgfip.finances.gouv.fr

For any question (which revenues to declare, which fields to fill in) you can:

Contact your local tax office (https://lannuaire.service-public.fr/recherche?whoWhat=Service+des+imp%C3%B4ts+des+particuliers+SIP&where=Paris+75) or the service des impôts des particuliers non-résidents

Call Impôts Service from Monday till Friday from 8AM till 10PM and on Saturdays from 9AM till 7PM: +33 (0)8 10 46 76 87

Meet a certified public accountant from May 22nd to May 25th at Ordre des experts-comptables de Paris (free of charge service, no appointment required): http://www.oec-paris.fr/qui-sommes-nous/contact-et-acces/contact-et-acces---2281

Meet a lawyer on Thursday, May 3rd in your local city hall (free of charge service, no appointment required): https://www.paris.fr/actualites/stresse-par-votre-declaration-de-revenus-un-avocat-vous-aide-4725

Good to know:

If you declared your income last year and you received your numéro de déclarant en ligne then you can declare online here: https://cfspart.impots.gouv.fr/LoginMDP?op=c&url=aHR0cHM6Ly9jZnNwYXJ0LmltcG90cy5nb3V2LmZyLw==

You may be income tax exempt thanks to some tax agreements between France and other countries. You can find a list of these tax agreements here: https://www.impots.gouv.fr/portail/les-conventions-internationales