As money is a sensitive matter, Lydia is legally required to make some checks.The Banque de France's ACPR (namely "Autorité de Contrôle Prudentiel et de Résolution") makes this very clear.
Lydia is made to simplify stuff. Therefore, we reduced identification requirements to a very minimum when creating an account. Users won't need to provide anything apart from their name and phone number. There will however be certain limits to their use of the app.
To use the app without limits, users will have to verify their account. This is simply a legal requirement to enjoy the very best of Lydia — of course, no personal information provided will be used.
In some very rare and specific cases, Lydia will be legally obliged to ask users for a document proving the origin of funds coming into their Lydia account. This is notably the case for very important or unusual sums.