Archiving Your Faxes: Preserving Evidentiary Value for 10 Years

Short answer: a fax doesn't lose its value because it's old, but because it's been poorly preserved. Since the ordinance of 10 February 2016, article 1379 of the French Civil Code grants a reliable copy the same evidentiary weight as the original — provided it offers an "identical reproduction of the form and content of the instrument, whose integrity is guaranteed over time." Decree no. 2016-1673 of 5 December 2016 spells out what that guarantee entails: digital hash, timestamping, traceability. In practice, this means three things: keeping the transmission report together with the document, freezing the files in a stable format accompanied by a hash, and maintaining an event log showing that nothing has changed. Without that, a fax PDF sitting in a shared folder is just another file.

The real risk isn't the sending, it's the five years that follow

A great deal of attention goes into the moment of transmission: checking the number, preparing the cover page carefully, obtaining an "OK" report. Then the document disappears into a network folder, an inbox or a cardboard box. Three years later, when a dispute arises, you discover that the transmission report has vanished, that the PDF has been renamed, that no one knows who opened it or whether it was altered.

A judge, however, doesn't think in terms of "file exists / file doesn't exist." A judge thinks in terms of credibility. A document produced late, with no metadata, no trace of its journey, bearing a file date later than the events at issue, will be challenged by the opposing party — and often successfully. As we detailed in our analysis of the evidentiary value of a fax before a judge, the probative force of a fax depends entirely on its documentary environment. Archiving is that environment.

Three scenarios come up constantly in law firms:

• The transmission report was printed, stapled to the paper file, and then the paper file was scanned without the report because it was considered a "technical receipt."
• The received fax was converted to PDF by the fax server, then automatically deleted after 90 days by a retention policy left at its default setting.
• The document was indeed preserved, but in a proprietary format (compressed multipage TIFF, the format of an abandoned document management system) that no tool in the organisation can still open in 2026.

None of these three cases is an accident. They are all failures of archiving policy.

What the law on digital copies actually says

Article 1379 and its implementing decree

Article 1379 of the Civil Code sets out the principle: "A reliable copy has the same evidentiary weight as the original." It adds that reliability is presumed — meaning it falls to the opposing party to challenge it — when the copy results from a reproduction meeting the conditions laid down by decree.

Decree no. 2016-1673 lists those conditions. It requires the reproduction to be faithful and durable, which entails:

• an electronic hash ensuring that any subsequent modification of the copy is detectable;
• either an advanced or qualified electronic signature, an electronic seal, or any process offering equivalent guarantees;
• a timestamp meeting the requirements of the European eIDAS regulation (EU regulation no. 910/2014);
• storage under conditions that prevent any alteration, with traceability of operations.

Note the key word: presumption. If you tick these boxes, it's up to the other party to demonstrate that your copy has been tampered with — a difficult task. If you don't tick them, the copy remains admissible (evidence is freely admissible for legal facts, article 1358), but it's up to you to convince the judge. The difference in procedural comfort is considerable.

The NF Z42-013 standard and its international counterpart

The NF Z42-013 standard, published by AFNOR and adopted internationally under the reference ISO 14641, sets out the specifications for an electronic archiving system (EAS) with evidentiary value. It is not mandatory in itself, but it is the benchmark that court-appointed experts and auditors use to assess a setup.

Its structuring requirements:

The NF Z42-026 standard completes the framework for the faithful digitisation of paper documents — the one that concerns you if you scan a fax received on thermal paper in order to add it to a digital file.

The Service interministériel des Archives de France (SIAF) also publishes reference frameworks and handbooks on electronic archiving in the public sector, useful even for private organisations: they set out, in particular, the notion of a document's "chain of trust."

The special case of thermal paper

Many older fax machines still print on thermal paper. This medium fades: under the effect of heat, light or simply time, the ink pales until it becomes illegible within a few years. A fax received in 2020 on thermal paper and stored in an exposed binder may today be nothing more than a grey rectangle.

The rule is simple: digitise immediately any fax received on thermal paper, meeting the reliable-copy requirements, and keep the paper for as long as it remains legible. Digitisation carried out on the day of receipt, with a timestamp, is infinitely better than digitisation done three years later on a degraded document that the opposing party can dismiss as illegible and therefore unreliable.

How long should you keep what

There is no such thing as a "fax retention period." The duration depends on the content, not the channel. The periods below are those commonly applied, drawn from the Commercial Code, the Civil Code, the Labour Code and the Public Health Code; the service-public.fr portal publishes a regularly updated summary.

Two principles govern how to read this table.

First principle: retain at least until the applicable limitation period has expired. There is no point destroying supporting evidence if you can still be sued on that basis.

Second principle: the GDPR prohibits indefinite retention. Article 5.1.e of the regulation imposes storage limitation. A fax containing personal data — and most do — must be deleted or archived in restricted form once the purpose has been fulfilled. The CNIL recommends distinguishing three phases: active base, intermediate archiving (restricted access, justified by a legal obligation or possible litigation), and definitive archiving or deletion. Keeping documents "just in case," with no defined period, is a compliance failure in itself.

For health documents, this tension is especially acute: the periods set by the Public Health Code are long, but access must be strictly limited. We covered these specific obligations in our article on medical faxes and health data.

Building an archiving chain that holds

What to keep together

An archived fax on its own is worth almost nothing. What makes the evidence is the bundle. Systematically keep, within a single archival unit:

1. The transmitted document itself, in its exact state as sent (PDF/A preferably).
2. The cover page, dated, with sender, recipient and number of pages.
3. The transmission report: date, time, number dialled, number of pages transmitted, duration, result indication, and, if the machine provides it, the recipient fax machine's identifier (CSID).
4. The send log for the period, which places the transmission within a coherent sequence of activity.
5. Any acknowledgement of receipt: a reply by fax, a confirmation email, a phone call recorded in a dated note.

It is the accumulation of these concordant elements that turns an isolated document into evidence that is difficult to challenge.

The technical move: hashing and timestamping

In practical terms, as soon as the file is created:

• Generate a SHA-256 hash of each file and record it in an index file that is itself timestamped.
• Have the whole set timestamped by a trust service provider. The list of qualified providers in France is published on ANSSI's Trusted List and on the European trusted list maintained by the European Commission.
• Ideally, apply an electronic seal of the legal entity (organisation), which is better suited than a personal signature for a repetitive document flow.

These operations are no longer the preserve of large organisations: most digital safe solutions and online fax services include them natively. Simply check, in the terms of service, that the timestamping is genuinely eIDAS-qualified and not merely a "date" field recorded by the software.

The event log

This is the item experts look at first and the one organisations most often forget. The log must record, in a tamper-proof way: the deposit of the document, every consultation with the user's identity, every export, every format migration, every hash verification, and the final destruction. A properly maintained log makes challenging integrity practically impossible.

Format migration

Ten years is a long time on a software timescale. A durability policy provides for periodic integrity checks (recalculating hashes at least once a year) and documented migrations to formats that remain readable. Every migration must be recorded in the log, keeping both the previous and the new hash. A silent migration is a break in the chain of trust.

The five mistakes that ruin an archive

1. Storing is not archiving. A shared folder, a NAS, a consumer cloud service: these are storage spaces. Files there can be modified, moved and overwritten. No presumption of reliability attaches to them.

2. Renaming files. Every rename alters the metadata and weakens the coherence of the file. Names must be fixed on ingest and never change; search needs are handled through index metadata, not file names.

3. Keeping only the "clean" PDF. Many organisations rescan or reprint a fax to obtain a more legible document and discard the original. In doing so, they lose the material trace of the transmission.

4. Leaving retention at its default setting. Fax servers and fax-to-mail gateways often purge after 30, 60 or 90 days. That value must be decided according to your retention schedule, not inherited from a factory configuration.

5. Confusing backup with archiving. A backup exists to restore a system after an incident; it is overwritten on rotation. An archive exists to prove; it is frozen. Both are necessary and neither replaces the other.

Frequently asked questions

Is a fax archived as a PDF enough in court?

It is admissible, but its evidentiary force depends on what accompanies it. A standalone PDF, with no transmission report or timestamp, will be treated as a mere indication. The same PDF accompanied by its transmission report, timestamped by a qualified provider and deposited in a traceable system, benefits from the presumption of reliability under article 1379 of the Civil Code.

Can I destroy the paper original after digitisation?

Yes, if the copy meets the conditions of the decree of 5 December 2016 (reliable copy). It is even recommended for thermal paper, which degrades. One caveat, however: certain instruments require the signed original to be kept — notably authenticated deeds and certain title documents. If in doubt about a binding document, keep the paper.

Do I need a certified electronic archiving system?

NF Z42-013 / ISO 14641 certification is not a legal obligation, unless specific sector regulations apply. It is, however, a very solid argument in the event of a challenge, and it is often required by public-sector clients. For a small organisation, a digital safe compliant with the NF Z42-020 standard already offers a serious level of assurance.

How long should a transmission report be kept?

As long as the document it relates to. The report is only of interest when paired with the fax: separating them, or applying a shorter retention period to the report, means depriving the document of its proof of transmission at the very moment you would need it.

Does the GDPR require me to delete faxes I am legally required to keep?

No. Article 17.3.b of the GDPR expressly provides that the right to erasure does not apply where processing is necessary for compliance with a legal retention obligation. You must, however, restrict access to these archives and document the legal basis for their retention in your record of processing activities.

Is a fax sent from an online service better archived?

Often yes, because such services automatically generate a timestamped acknowledgement and keep a server-side log. But check two points in the terms and conditions: the retention period offered, and the ability to export your evidence. A log you cannot extract will disappear along with the provider. The specifics of each service are detailed in our frequently asked questions.

In summary

• Article 1379 of the Civil Code and the decree of 5 December 2016 make a reliable copy the equal of the original: hash, eIDAS timestamping, traceability.
• The NF Z42-013 / ISO 14641 standard defines the archiving system with evidentiary value; NF Z42-026 governs faithful digitisation.
• The retention period depends on the content, not on the fax: 10 years for accounting records, 5 years under general law, 20 years for a hospital file.
• The GDPR imposes storage limitation: define three phases (active, intermediate, definitive) and document them.
• Archive the fax together with its cover page, its transmission report and the send log: it's the bundle that makes the evidence.
• Immediately digitise any fax received on thermal paper, which fades within a few years.
• Never confuse storage, backup and archiving: only the third is designed to prove.