Archiving your faxes in 2026: retention periods, formats and proof

Short answer: in 2026, a fax is not archived the way a paper letter is. What gives a fax its value before a judge or an inspector is not the thermal sheet filed away in a binder — it is the triplet of document + transmission report + timestamp, kept together, in a format that will still be readable ten years from now. Retention periods themselves do not depend on the channel: a purchase order remains a purchase order, whether it arrived by fax, by e-mail or by post — meaning 10 years for accounting records, 5 years for most commercial contracts, 3 years for routine tax documents. The only thing the fax adds is a requirement of method: without a transmission report archived alongside the document, you are keeping a piece of paper, not a piece of evidence.

The subject looks like pure paperwork. It becomes urgent the day a customer disputes ever having received a formal notice, when URSSAF asks to see a declaration sent three years earlier, or when a medical practice has to account for a report sent to a colleague. At that moment, two companies out of three discover that their "archived" faxes are either illegible thermal prints, or PDFs scattered across a shared mailbox, or files still sitting on the hard drive of a multifunction fax machine that was scrapped last year.

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What the law actually requires you to keep

First clarification: no French legislation imposes a retention period specific to faxes. The Commercial Code, the Book of Tax Procedures and the Civil Code all reason in terms of document type, not transmission channel. The fax is merely a means of delivery, no different from a stamped envelope.

The reference periods, as set out notably on the entreprendre.service-public.fr portal:

Second, subtler clarification: the useful retention period is often longer than the legal one. A fax terminating a contract sent in 2026 may still matter in 2031 if the dispute involves a five-year limitation period. The practical rule adopted by most legal departments is simple: align everything on 10 years, except for sensitive personal data, for which the CNIL requires, on the contrary, a limited and justified period. Keeping things "just in case" is no virtue when health or HR data is involved.

The special case of personal data

The GDPR does not say "keep little", it says "keep for as long as the purpose requires, then purge or archive". A fax containing a set of test results, a payslip or a job application falls within this scope. In practice this imposes three things: a period defined by category, an archive with restricted access (the archive is not the whole department's mailbox), and effective deletion at the deadline — including in backups, which almost nobody does properly.

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The transmission report: the piece everyone forgets

This is the heart of the matter. French case law on the evidential value of faxes has been consistent since the 2000s: a fax is a prima facie written evidence or, in commercial matters, an element of freely admissible evidence, but it only counts if the sender can establish that it was indeed transmitted to the right number, on a given date, with a given number of pages. In other words: the document on its own proves nothing. It is the transmission report that turns a PDF into evidence.

A usable report contains at minimum:

• the number called in full format (country code included);
• the date and time transmission ended, with the time zone;
• the number of pages transmitted — and it must match the document;
• the status (OK / failed / partial) and, ideally, the T.30 termination code;
• the duration of the call;
• often, the remote machine's CSID identifier, which confirms that you reached the intended recipient and not a recycled number.

On a conventional fax machine, this report prints on a separate sheet that invariably ends up detached from the document. That is the structural weakness of paper faxing. With an online fax service, the confirmation arrives by e-mail and can be stored in the same folder as the document — provided you do it systematically, not case by case. If you still send from a fax machine, set it to print the report with a reduced image of the first page: most models offer this option, and on its own it solves the matching problem.

For critical transmissions, one simple, robust practice: create a folder per transmission containing the source document (the one you signed and scanned), the fax as it was sent, and the report. Three files, one standardised folder name such as 2026-09-17_client-durand_formal-notice. On the day of the dispute, you produce a coherent set rather than a pile of clues.

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Thermal paper, PDF, PDF/A: choosing the format

Why thermal paper is a trap

The thermal paper of old fax machines darkens under the effect of heat, light and time. Depending on storage conditions, a document becomes partly illegible within two to five years — sometimes less if it has been sitting in a binder near a radiator or behind a window. A fax from 2022 kept that way may already be unusable today. And an illegible document proves nothing.

If you still hold thermal archives, the only useful action is to digitise them without delay. A duplex scanner with an automatic document feeder handles a few hundred sheets per hour and costs less than half a day of a lawyer's time. For large holdings, outsource: archiving providers charge by the page and deliver an indexed PDF.

The right target format: PDF/A

For long-term archiving, the standard is PDF/A (ISO 19005), a format designed for durable preservation: embedded fonts, no external content, no JavaScript, rendering guaranteed for decades. The Archives de France and the French interministerial archiving framework recommend it explicitly. Most online fax services deliver a standard PDF; converting to PDF/A when depositing into the archive takes ten seconds with any serious PDF tool.

Two settings matter as much as the format:

• Resolution. A fax received in "standard" mode (204 × 98 dpi) is often barely legible. Ask your correspondents to send in fine mode (204 × 196 dpi) for anything containing figures, signatures or handwritten notes. We cover these settings in detail in our guide to illegible faxes.
• OCR. A fax is an image. Without character recognition, your archive is not searchable: finding "the Dupont order from March 2024" means opening files one by one. An OCR software package applied at deposit makes the holding searchable in full text while preserving the original image beneath the text layer.

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Where to store it: three architectures that work

1. The disciplined local archive

A network folder structured by year / entity / type, backed up according to the 3-2-1 rule: three copies, on two different media, one of them off site. In practice: the server, an encrypted external hard drive rotated every week, and a remote repository. It is the cheapest option and the most fragile — it relies entirely on human discipline. It suits organisations of fewer than ten people with a clearly identified person in charge.

One point that is often overlooked: media age. An external hard drive left in a drawer for six years has a far from negligible chance of never spinning up again. Rotate every three years at minimum, and check the readability of a sample each year.

2. The digital vault / electronic archiving system

Evidential electronic archiving services apply the NF Z42-013 standard (and its international counterpart ISO 14641): a cryptographic hash of each file on deposit, a tamper-proof event log, full traceability of access. This is what regulated sectors look for — healthcare, insurance, regulated professions. The extra cost is justified as soon as you are archiving documents whose contestation would cost more than the service itself.

3. Archiving built into the fax service

Most fax-to-email offerings retain a history of sent and received items for a contractual period. It is convenient and immediately usable, but it is not an archive: the period is often shorter than your legal obligations, and access disappears along with the subscription. Treat it as a lookup tool, not as preservation — and export periodically. If you are new to receiving faxes by e-mail, our fax-to-email guide explains how documents arrive and in what format.

In every case, encryption at rest is not a luxury: a folder of medical or HR faxes on an unprotected external drive is a data breach waiting to happen. A hardware-encrypted external hard drive, or simply the encryption built into the operating system, is enough to rule out the stolen-equipment scenario.

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What you really must not do

Leaving faxes in the mailbox. A shared fax@company.com mailbox is not an archive: quota reached, accidental deletion, the account holder leaves, mail migration — the opportunities to lose everything are endless. Mail systems also apply automatic retention policies that nobody ever reads.

Relying on the multifunction device's drive. Recent fax machines and MFPs store received faxes on an internal drive. That drive leaves with the machine when it goes back to the trade-in provider — documents included, which is also a major confidentiality risk. We mentioned this in our article on end-of-life fax machines.

Archiving without an index. Ten thousand PDFs named fax_00347.pdf make a heap, not a collection. A standardised naming convention (ISO date, correspondent, subject) or a simple index spreadsheet changes everything — and costs a few seconds per document.

Confusing backup with archiving. A backup protects against failure and is overwritten in a loop over a few weeks. An archive protects against oblivion and is kept for ten years. Both are necessary; one never replaces the other.

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Setting up the procedure in half a day

1. Take stock. Where do your faxes arrive today? Paper, mailbox, MFP drive, the service's web interface? List every entry point — there is usually one more than you expected.
2. Decide on a single archiving point. One root folder, one tree structure. Everything else is temporary.
3. Set the periods by category, using the table above, and write them down in a one-page note. An unwritten procedure does not exist.
4. Standardise naming and make the trio of document + report + timestamp mandatory for transmissions that matter.
5. Digitise the remaining thermal stock before it fades away.
6. Test retrieval. Ask someone who did not build the archive to find a specific fax from last year in under three minutes. If they cannot, the archive is decorative.
7. Schedule the purge. An annual review, on a fixed date, deleting anything past its retention period — a GDPR obligation and basic hygiene.

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Frequently asked questions

Is a fax that has been scanned and then destroyed in paper form still valid?

Yes, subject to conditions. The digital copy of a paper document has the same evidential force as the original if the reproduction is faithful and durable (article 1379 of the Civil Code), which presupposes compliant digitisation — AFNOR published the NF Z42-026 standard precisely to frame this "reliable copy". In practice: scanning in colour or greyscale, sufficient resolution, hashing and timestamping at capture. For high-stakes documents, keep the paper anyway.

Should failed faxes be archived as well?

For legally significant transmissions, yes — and it is counter-intuitive. A failure report proves that you attempted transmission on a given date, which can be decisive if the recipient claims they heard nothing. Keep the full series of attempts in the same folder.

How long does an online fax service keep my documents?

It depends on the contract, generally from a few months to a few years. Check it in the terms and conditions and, above all, never base your legal compliance on it: export to your own archive. Questions of coverage, pricing and retention are addressed in our frequently asked questions.

Does a handwritten signature sent by fax carry any weight?

It does, but only limited weight: the fax degrades the image to the point where handwriting analysis is rarely conclusive. For a significant commitment, the fax serves to start a deadline running or to formalise something quickly; the signed original or a qualified electronic signature must follow.

Do I need to timestamp my archived faxes?

For the vast majority of documents, the timestamp on the transmission report is enough. For documents whose date determines a right — contract termination, a response within a deadline, a claim — a qualified eIDAS timestamp provided by a trusted third party removes any argument about precedence.

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The key takeaways

• The retention period depends on the type of document, not on the fact that it arrived by fax: 10 years for accounting, 6 years for tax, 5 years for most commercial matters.
• Without a transmission report archived with the document, you have a piece of paper, not evidence.
• Thermal paper fades within a few years: digitise the existing stock now.
• Aim for PDF/A with OCR, a standardised naming convention and the 3-2-1 backup rule.
• Your online fax service's history is a lookup tool, not an archive: export regularly.
• Test retrieval at least once a year — an archive you do not know how to query is useless.
• Schedule the purge: keeping data longer than necessary is a GDPR risk, not a precaution.

You can send your next fax directly from the sending form and immediately file the confirmation you receive in the relevant case folder: it is the simplest way to archive without even thinking about it.