People born in France are attributed a social security number at birth and receive a carte vitale showing this at age 16. It is proof that you are affiliated to French social security and is needed for healthcare reimbursements and as part of formalities for working.
EU citizens who arrive in France without one may initially use a European Health Insurance Card (Ehic) for healthcare and if they are pensioners with an S1 form they should present this to their local Caisse primaire d’assurance maladie (they do not need a French social security number).
Otherwise to obtain a carte you can apply to the Cpam using this form: tinyurl.com/y9htm46s
You need to supply a copy of your passport and birth certificate (EU regulations say Europeans should not need translations for this). The application is to the Mutualité sociale agricole for farmers or to the relevant social security body for the self-employed for independent and other self-employed people.
It is possible for employees to be taken on without a number, in which case the employer can make the application for them as part of the hiring formalities.
In the first instance we suggest your daughter registers as a jobseeker at Pôle Emploi to show she is living in France and is looking for work.
If she has any right to UK jobseekers’ allowance this can continue for three months after moving to another EU country so this applies for France.
A social security number has 13 figures, starting with a 1 for men and a 2 for women. The rest relate to year and month of birth, place of birth (those born outside France have 99 plus a 2-digit country code) plus other figures to distinguish you from people born at the same time and place.