Certain administrative procedures require the submission of documentary proof in the form of certificates or attestations.

An attestation is a declaration in which an organisation attests to the existence or truth of a fact.

A certificate is a type of attestation. Carrying more official weight than a standard attestation, a certificate is a document issued by a competent authority to attest a fact or a right. Thus, communal administrations are authorised to issue residence certificates providing information on the applicant's place of residence, whilst certificates of nationality are issued by the Ministry of Justice (Ministère de la justice) to persons holding Luxembourgish nationality.

Similar in weight and effect to certificates are legal deeds for civil registry entries (deeds, for example, attesting to a birth), as well as legalisations of documents (certifying the origin of a document) or of a signature (certifying the authenticity of the signatures on a document or deed).