you have to fill in a “day-month-year” thingy…
Surely, you must know when you bought. 
that’s a starting point… after that things should get easier 
An electricity contract is another way of dating… if it shows your French address on the bill and NOT the UK (or wherever)
where did you come from ???
It is the day we cannot remember, can I put a random day, can they check?
Yes, we have the purchase attestation.
UK
Righto, so your property doc gives you the earliest possible date.
Bearing in mind that one can live in Europe for some months before “deciding” to be permanent - I reckon you can come up with your own date… so long as the Tax things will support you. Check your Taxe d’Hab bills. They should show the address as Main or Second residence…
Stella,I think I have gone around in a circle
Following Dans’ advice I will just add explanations in the comments box.
Whats a day here and there
Sounds like a plan.
At least getting something “done” is a step forward and the powers-that-be can (and will) ask for any other info they need…
All will be well in the end - 
I didn’t say they didn’t, I was just making the point that the French authorities are not going to be too concerned about the actual date if it was than more than five years ago so as long as you know the year and the month. This is just the registration phase, you’ll likely to be asked to produce more documents when/if the applications are processed.
I agree with @tim17
On that basis, if you know you moved in month xxx but can’t remember which day (and it’s over 5 years ago) then I’d be tempted to say the 1st of month xxx +1 which means you are not claiming an earlier period than the actual.
If over 5 years, the actual day/month/year is academic and unlikely to raise eyebrows or cause sucking of teeth 
Just don’t fret about it - the stress will do you no good.
Stella Graham and Tim
We need a sucking of teeth/shoulder shrug emoji’s 
If you have an approximate idea, that vaguely matches banks statements then just write an attestation sur l’honneur that you arrived on x date. This is what we did roughly 3 months after arrival for our application for CPAM (give or take a week or so perhaps) and it is what we use as “the” date.
You do not require a CdS, and the Préfecture will not action your request when they receive it.
As a consequence of the Brexshit nonsense, France has decided to introduce an entirely new ‘residents permit’ specifically for Brits. Your need not apply for it yet - you have 6 months after whatever deal is done. See details at gov.uk/livinginfrance
What a confusing post. It’s also worth pointing out that the application process reached by your long winded link will want to know the date that you arrived in France.
Have you completed a tax return? On the first one that you fill in you have to give the day that you arrived in France. If so do you have a copy?
Sorry, Dan - are you saying my post was confusing? Or the OP?
Your post.
For a start the topic has been covered in great length on another thread started about 10 days ago and the process involved is talked about by posters replying on this thread.
You then say there is no need to apply for a CdS yet give a link to apply for a CdS.
Next you give a gov.uk link which takes you to a page which has the gouv.fr link instead of going directly to the French site.
Finally you say that is for when the deal is done when in fact it is the route to take if there is a no-deal Brexit.
I found it confusing.
Threads will wander… each person gives what they can
and, yes, information is often repeated, sometimes several times…
That’s just how it goes… for example, more than one person has mentioned the Tax Return … 
Please can we all relax and not heckle one another… 
Im aware that you mentioned the tax return but you also seem to have been under the impression that the OP and her OH moved at the same time and did a joint initial tax return. In the headline post it’s made clear that the OP arrived several years after her OH so I thought that mentioning her first return, was important.
I still maintain that the other post is very confusing but perhaps it’s just new non British posters like me who don’t understand the system. I guess I will go back to lurking and give contributing a miss. I hope it all works out fine for you all.
Sorry Dan - but now you are confusing me! The link that I gave does not take you to any gouv.fr link. It is the current UK Government guidance specifically for Brits living in France.
The situation is actually very clear now, thanks to the French - who have designed a specific solution for the situation that we find ourselves in.
Everybody will need a new ‘Residence Permit’. If you have an existing Carte de Séjours you will have to exchange it for the new permit. The French site (confusingly!) refers to the new card as a Carte de Séjours. But for the OP, who is struggling with an application for (I have assumed) the existing CdS , they can forget it. Wait for Brexit to happen. Then apply online for the ‘new’ card. Since the website is already up-and-running (very sensibly, so that they can sort out any technical glitches in advance) you can sign up online now if you want to - but applications will not be dealt with until the event. They have allowed 6 months after Brexit to deal with applications. Remains to be seen whether the system and manpower availability will cope - it wasn’t the French who asked for this workload!
To try to clarify a bit further. Currently, as a member state of the EU, British citizens are not required to have a Carte de Séjours - this is a documentary requirement for non-EU country residents. Earlier on in the Brexit cock-up, however, the British Government jumped the gun, and recommended all Brits to apply for the existing CdS - but the French have over-ruled this by creating a Brit-specific residency card, regardless of the outcome of Brexit.
It took me to here by following the path to information on residency;
To get back on topic…
It is confirmed that the on-line setup for Brits does ask for a date on which one considers oneself Permanent. dd-mm-yyyy
so figure on a date which seems to make sense - if one has been here more than 5 years. (but try to have an even vague paper backup).
and there is always the box for extra explanation…
Best of luck everyone…
