The documents or supporting documents necessary for the establishment of the basis of assessment or for the control of social security contributions must be kept for a period of at least six years from the date on which the documents or documents were drawn up or received.

When documents or exhibits are drawn up or received on paper, they may be kept on a computer medium. The procedures for digitising documents drawn up or received on paper are set by order of the Minister responsible for social security.

Book of tax procedures, Section A102 B-2

I. – The transfer of invoices originally drawn up on paper to a computer medium is carried out under conditions guaranteeing their identical reproduction. The result of this digitization is the copy conforming to the original in image and content. The colors are reproduced identically if a color code is implemented. Image processing devices are prohibited. If file compression is used, it must be lossless.

II. – Digital archiving can be carried out by the taxable person or by a third party mandated for this purpose. The digital archiving operations of invoices originally drawn up on paper are defined according to a documented organization, subject to internal controls, ensuring the availability, readability and integrity of the invoices thus digitized throughout the duration of conservation.

III. – In order to guarantee the integrity of the files resulting from the digitization, each digitized document is kept in PDF format (Portable Document Format) or in PDF A/3 format (ISO 19005-3) in order to guarantee the interoperability of systems and the sustainability of data and is accompanied by:
1° A server stamp based on a certificate that complies with at least the one-star level general security reference system (RGS).
2° A digital fingerprint.
3° An electronic signature based on a certificate that complies, at least, with the general security reference system (RGS) at one-star level.
4° Or any equivalent secure device based on a certificate issued by a certification authority appearing on the French trusted list (Trust-service Status List-TSL).
Each file is timestamped, at least by means of an internal timestamping source, in order to date the various operations carried out

Source: https://www.legifrance.gouv.fr/codes/article_lc/LEGIARTI000037853712/ 

https://www.legifrance.gouv.fr/codes/article_lc/LEGIARTI000034311685