Of all the administrative challenges of moving, working out how to complete a tax return in France was probably the hardest part. There is little information online and all of my colleagues said that they paid someone to do it for them.
I found out quickly that the tax year runs from January to December. Fine, this seems more sensible than the UK’s April deadline. What was less obvious was that you cannot submit your return for the previous year (I will talk about this as 2018, as this is the first year I did so) until April or May of the next year.
The situation changed slightly the year after I completed my first form – they are now encouraging everyone to submit their first tax return online. This page on their site asks “Can I declare on line for my first declaration”? https://www.impots.gouv.fr/portail/particulier/questions/puis-je-declarer-en-ligne-pour-ma-premiere-declaration-de-revenus
The fourth section of this page probably applies to you: you don’t already have a fiscal number.
Apparently, you should go to the contact page of the tax website: https://www.impots.gouv.fr/portail/contacts
And fill it in as follows:
Which should bring up the following information:
Click “accès au formulaire” and you will reach the following form:
And hopefully, this will get you the required fiscal number. I never did this myself because it wasn’t an option – I had to send a paper copy. If you prefer, the paper copy is still an option according to the final paragraph of the section quoted earlier: