Does anyone have a similar dilemma?
I’m a UK citizen wishing to retire to my house in France (that I have owned for many years) and hoping to get a Carte de Sejour (due to the Brexit).
My financial base / retirement income is derived from a country (not the UK) that has a taxation treaty with France (ie tax payable at the income source only and not in France).
Does this mean I do not need to submit a ‘nil’ tax return in France? If not how would that affect an application for a Carte de Sejour?
I’m not a tax expert by any means Alec but over the years I have had a fair amount of tax advice on living in France with foreign income, including from KPMG. Basically if one spends more than 180 days a year in France or France is your domicile (a complex subject in its own right) you should make a tax declaration. Obviously, depending on the provisions of the DTA, you will get credit for tax paid in the source country. Regarding a CDS I would suspect all that matters is that you can prove you can support yourself and not become a burden on the French social welfare or public health system.
In order to qualify for a carte de séjour you need to be residing in France in a stable and regular (ie respecting all the rules) manner.
One of France’s rules is that all residents submit an annual declaration of income
I’m not exactly sure what your question is, but if you combine those two facts you’ll probably find you have answered it.
To expand a little - your income declaration isn’t only about income tax. It’s also used to calculate your RFR (total taxable income figure) which crops up in various circumstances, for instance it’s used to calculate your taxe d’habitation, and it’s also used to determine any state benefits you can apply for eg. certain grants towards energy saving home improvements. Your income declaration is also used by URSSAF to calculate your health service contributions if you’re living here as a self-supporting inactif. And it’s used to calculate any CSG/CRDS that you may have to pay; this is a social charge and in some circumstances you may have to pay this, even though under an international treaty your income is not taxable as such in France.
As John said, as a resident you must declare worldwide income in France, which means you declare all income from all sources and countries, regardless of where it’s taxed. The fisc then apply the relevant tax treaty/treaties. It’s not for the individual to decide what income to tell the fisc about.
Hope this helps clarify.
I seem to remember you had a second home here. So have you now moved over?
You can only get a CdS if you have been permanently resident for at least three months, are in the health service (or have private health insurance), and have sufficient finds to support yourself. And french residents have to fill in a tax return, as Anna has clearly explained even if you have no tax to pay it is important particualry to show you can support yourself.
With B**** less than three months away if you are not resident now you will need to get things in order if you want to avoid immigration procures. However I seem to recall reading that as long as you can prove you were fully resident by B***** day, you won’t then have to go through the immigration procedures for non-EU nationals. And can presumably apply for CdS later. How you prove you were resident if you’ve not done tax returns, and still have taxe d’hab as maison secondaire is another question!
I think the position will be that newcomers can apply for a one-year CDS, which I think is quite easy to get although I don’t know exactly what it entails, and that will allow them to stay in France and have an opportunity to “clock up” their five years legal residence. The important thing for them will be to get their ducks in a row and ensure they consistently meet the conditions so that five years down the line, when it’s time to apply for their full CDS, they have all the necessary paperwork dating back to the time they claim to have arrived, ie prior to B-day. So if they say they arrived in February 2019, they will in due course need to show paperwork proving they declared their 2019 income, had healthcover in place during 2019, etc.
That seems to be the plan but of course until Brexit happens nobody can say for definite.
EDIT - thinking about it, I guess the paperwork will be checked year by year when they go along to renew their temporary CDS, so in fact you wouldn’t get up to the 5 year mark if you hadn’t met the conditions in one of the earlier years. But I don’t really know.
It was carefully explained to me at the Tax Office, when we made our first Declaration… (I was so worried about being taxed twice… despite the Treaty.) 
You tell us everything, Madame, and we will calculate your Tax Liability for France…then we look to see what you have already paid (in the other country) …
and… if you have not paid enough by our calculations… then we ask you for that bit extra 
… BUT… if you have already paid too much, by our calculations… NO, we do not give you any back… sorry. 
As has been said , everyone tax resident in france is required to make a declaration of their total worldwide income (with a few very specialised exceptions). It also serves to register you for paying (or not ) a TV license fee. When required to prove years of residence to qualify for a full 5 year or permanent carte de sejour a tax demand -even for nil tax- is usually asked for , for each year of residence . This will surely apply also to any post -B arrangements.
The tax authorities will apply any treaty conditions. If the country of origin of your main income is a lesser known one , you should read the treaty carefully , so as to check that the fisc have applied it properly - they have been known to make mistakes.
The good news is that any DTAs I’ve read have actually been quite straight forward.