Are we obliged to make accessibility declaration?

This is, in fact, a commercial company, offering paid services that are marketed as helping businesses comply with the latest rules on accessibility to disabled people (new ones came into force recently).

As such you are not obliged to reply to the letter and in any case the new accessibility rules only apply to businesses that are open to the public (eg. a bakery) so it is unlikely they would apply to your daughter’s micro-entrepreneur business, especially if it has no separate premises.

Government officials put out a warning about this ‘agency’ earlier this year, to the effect that it is not necessary to pay for such services to comply with the rules.

For firms which are affected, information on accessibility requirements can be obtained from your direction départementale des territoires (DDT) and there are also details at accessibilite.gouv.fr