Archiving your faxes: keeping evidence that holds up in 2026

Short answer: in 2026, the problem with fax is almost never the sending — it's what's left of it eighteen months later. A fax that went out correctly but whose transmission report was thrown away, overwritten, or left in an individual mailbox that has since been abandoned is worthless on the day you need to prove a document was received before a given date. Archiving a fax therefore isn't about "keeping the PDF": it's about preserving three linked elements — the transmitted document, the time-stamped technical acknowledgement showing the number dialled, and a record of the sender's identity — in a company-controlled location, for a period aligned with the limitation period applicable to the matter. The rest of this article explains how to do that without building a factory.

The situation is commonplace in law firms, public-procurement departments and HR teams: people know how to send, they know how to receive, they don't know how to retrieve. The transmission acknowledgement is a slip of thermal paper sitting on top of a pile of files, or an automated email filed in the "Sent Items" of a personal mailbox. Either way, the evidence exists on the day itself and has vanished by the day of the dispute.

Yet this is precisely the only reason fax still has any value. We've already written about this in relation to the legal standing of fax: what gives a fax its strength before a judge is the combination of content and a technical record. Break the link between the two and all you have left is a PDF like any other.

What you actually need to archive

The minimum triptych

A complete fax evidence file contains three items — not one fewer:

1. The transmitted document, in exactly the version that was sent — cover pages included, in order and with pagination.
2. The transmission report, i.e. the acknowledgement produced by the service: date and time, the full number dialled (country code included), number of pages transmitted, final status, call duration and, if possible, the session identifier.
3. Attribution, meaning who within the organisation triggered the send, and from which account.

The third point is the one people forget. An online fax platform where everyone shares a single login produces unimpeachable technical logs… that are incapable of saying which employee sent what. In the event of an internal challenge, or an audit of a flow containing health data, that's a serious blind spot.

What does not count as evidence

• A screenshot of the interface. Not verifiably time-stamped, cropped, re-encoded: it will be dismissed without difficulty.
• A "sent" entry in a tracking spreadsheet. That's the sender making a statement about themselves.
• A confirmation email where only the message body was kept, without the technical header or the attachment.
• The fax sent back by the recipient, unless it is itself traced.

The special case of receiving

On the receiving side, the logic is reversed: what you need to prove is not the send but the date of arrival. An incoming fax converted to PDF and deposited in a dedicated mailbox already carries a server receipt date, which is often sufficient. The guide on receiving a fax by email covers the configuration; from an archiving standpoint, the key point is that this mailbox must be a shared service mailbox, not an assistant's personal inbox.

How long should you keep them?

There is no such thing as a "statutory retention period for faxes". The duration follows from the file the fax belongs to. So you align fax archiving with the document it carries, not the other way round.

Two practical rules follow from this.

First rule: never keep the fax log longer than the file itself. A send history kept "by default, indefinitely" is a stockpile of personal metadata — who wrote to whom, and when — and therefore a processing activity that must be justified under the GDPR. The topic is developed in our article on fax and the GDPR: data minimisation applies to technical logs too.

Second rule: distinguish current retention from archiving. The last three months stay accessible in the service's interface for day-to-day management. Beyond that, the evidence file moves into the company's folder structure, filed with the matter, not with the tool. That way, when you change providers, the evidence doesn't leave with them.

Format: aim for legibility ten years out

PDF, PDF/A and the TIFF trap

Legacy fax machines produced Group 3 or 4 TIFF files. Online services deliver PDFs. For long-term archiving, the format recommended by electronic archiving frameworks — notably those of the Service interministériel des Archives de France (SIAF) and the NF Z42-013 standard, taken up internationally as ISO 14641 — is PDF/A, precisely because it embeds everything it needs to display identically twenty years from now: fonts included, no external dependencies, no active content.

In practice, for an SME, three decisions are enough:

• Keep the PDF exactly as supplied by the fax service, without re-saving it from a viewer that would recompress it.
• If a PDF/A conversion tool exists in your office software chain, use it for documents destined for archiving beyond five years.
• Never flatten an evidence file into a single image: the report and the document must remain separately identifiable.

Naming is already half of archiving

A meaningful file name beats a database nobody will maintain. The convention that works everywhere:

2026-10-05_DUPONT-SCI-LES-TILLEULS_fax-33123456789_envoi.pdf
2026-10-05_DUPONT-SCI-LES-TILLEULS_fax-33123456789_rapport.pdf

Date first in ISO format (automatic chronological sorting), then the matter, the number dialled, and the nature of the document. No accents, no spaces, no special characters: these files will survive several server migrations.

Paper is not an archiving solution

The thermal paper used by fax machines fades. Not "degrades": fades, within two to five years depending on exposure to light and heat. A thermal transmission report filed in a hanging folder near a window will be illegible before the limitation period runs out. If you want a paper trail, you need to photocopy or scan it, thermal paper being nothing more than a medium for immediate reading. For organisations still holding bundles of paper, a duplex document scanner with an automatic feeder makes this catch-up work bearable, and a batch of acid-free archive boxes stops the rest of the file yellowing around it.

Strengthening evidential value without over-engineering

Fax has a structural flaw: the acknowledgement proves that a transmission reached a number, not that a specific piece of content was received intact. Three simple steps substantially reduce that weakness.

1. Link the content to the report with a hash

Before sending, compute a hash of the PDF (a SHA-256 checksum) and record it in the file, next to the report. If the archived document is ever challenged, you can demonstrate that it is bit-for-bit the one that was transmitted. The operation takes ten seconds with the tools built into Windows, macOS and Linux; no software to buy.

2. Time-stamp sensitive batches

For high-stakes matters — litigation, procurement, estates — a qualified time stamp within the meaning of the European eIDAS Regulation provides a date that can be relied on against third parties, issued by a trust service provider listed on the French trusted list maintained by ANSSI. You don't time-stamp every fax: you time-stamp a monthly container holding that month's evidence files. The cost is marginal, the legal effect considerable.

3. Write a one-page archiving policy

This is the item auditors and lawyers ask for first, and the one that is almost always missing. One page is enough:

• who is allowed to send faxes, and from which account;
• where evidence files are deposited, and under what naming scheme;
• the retention period by type of flow;
• who purges, how often, and how the purge is recorded;
• who is responsible if the provider changes.

A written, dated document signed off by management turns a practice into a procedure. Before a judge, a procedure applied consistently carries far more weight than the single best piece of evidence. A lever arch file dedicated to the purge register, kept by hand, is plenty in a ten-person organisation.

Where to store it: three realistic scenarios

The micro-business and the sole practitioner

One folder per matter on a shared workspace, an automatic daily backup, and a quarterly offline copy on an encrypted external hard drive stored somewhere other than the office. The so-called 3-2-1 rule: three copies, two media types, one off-site. It's modest, and it's enough to see you through five years.

The multi-department SME

Folder structure by entity and by year, access rights restricted to the departments concerned, access logging enabled. Incoming faxes land in functional mailboxes, not personal ones — a point already covered in our guide to multi-site fax. For departments handling health or payroll data, a cross-cut document shredder next to the printer stops the paper version outliving the archived PDF.

The organisation subject to audit

An electronic archiving system compliant with NF Z42-013, sealed batches, a tamper-proof event log. In that case the fax flow becomes just one source among many: the online fax service deposits PDFs and metadata into the archiving system, which takes on responsibility for evidential value. This is the architecture adopted by most healthcare institutions and large local authorities.

In all three cases, one non-negotiable rule: the fax service is not the archive. It's a carrier. You don't hand your accounts over to your carrier.

The tricky moment: changing providers or closing a line

The shutdown of the legacy PSTN triggered a wave of migrations, and those are exactly the moments when evidence disappears. Before any cancellation:

1. Export the entire history — PDFs and logs — and check that the export is legible outside the tool.
2. Check a sample of ten older files: does the report clearly show the full number and the time stamp?
3. Document the switchover: end date of the old service, start date of the new one, whether the number was ported or not. A three-day, unexplained gap in a log is expensive five years later.
4. Keep the provider's final invoice: it proves the service existed on the dates in question.

If the number changes, notify in writing those correspondents who still send faxes, and keep that notification. For those who want to keep their old number, the subject is covered separately in our article on keeping your fax number. Covered destinations and their numbering formats are listed on the supported countries page.

Frequently asked questions

Is a transmission report enough to prove the document was received?

It proves that a communication reached a given number, at a given time, for a given number of pages. That's a solid starting point for evidence, weighed freely by the judge. Combined with a hash of the document and a consistent sending practice, it is hard to contest. On its own, without the corresponding document, it is worth almost nothing.

Can paper be destroyed after scanning?

Yes, in the vast majority of cases, provided the digital copy is reliable within the meaning of article 1379 of the French Civil Code: identical, durable, and produced through a documented process. The exceptions concern authenticated deeds and a handful of original title documents. For fax, where the original is a reproduction anyway, the question practically never arises.

Should failed faxes be archived too?

Yes, and it's often useful. A log showing three unsuccessful attempts to a number, followed by a successful send, documents the sender's diligence. Purely technical failures can be very telling, as we saw in relation to failed international sends.

Is a fax archived in an email mailbox properly archived?

No, not durably. Email is a flow tool: quotas, automatic purges, the account holder leaving, server migrations. The evidence file must live in the matter's document structure, alongside the rest of the file.

What period should you choose when you don't know?

Five years, the general limitation period in civil and commercial matters, covers most situations. Extend to ten years for anything touching on accounting, and align with the patient record for health-related flows.

Key takeaways

• An archived fax means three linked items: the document, the time-stamped transmission report, and the sender's identity.
• The retention period is that of the matter, never that of the tool: five years by default, ten years for accounting.
• A PDF kept exactly as received and named according to a stable convention beats any database nobody maintains; PDF/A is preferable beyond five years.
• Thermal paper fades within two to five years: it must be scanned, not archived.
• A SHA-256 hash and a qualified eIDAS time stamp on sensitive batches strongly reinforce evidential value at negligible cost.
• The fax provider is not the archive: export before any cancellation, and document the switchover.
• A one-page archiving policy, dated and actually applied, carries more weight than one perfect piece of evidence in isolation.

For implementation questions on the sending side, the FAQ answers the most common points, and the sending form remains accessible from the home page.