Short answer: a fax should be kept for as long as the document it carries — three years for a sales follow-up, five years for an invoice, ten years for an accounting record, twenty years for certain medical files. But a fax archived on its own is worth almost nothing: what you need to keep is the document + transmission report pair, in a format that will still be readable in ten years (PDF/A or TIFF), named systematically and backed up in two copies on two different media. The rest — thermal paper, output trays, ring binders — can disappear without regret.
This is the blind spot of going paperless. Many organisations have sorted out sending and receiving, they have abandoned the fax machine, they receive their faxes as PDFs in an email inbox… and three years later, nobody can find the fax from 14 March that proved the formal notice was served. Yet the document does exist, somewhere, in a message thread with 4,000 entries.
Archiving is not storing. Here is how to tell the difference.
Why faxes pose a particular archiving problem
Three very concrete reasons.
The original medium is perishable. Older fax machines printed on thermal paper: an ink that isn't really one, just paper darkened by heat. Exposed to light, to the warmth of a radiator, or simply to time, this paper yellows and then fades away. Case documents that are illegible after five years are not an urban legend: it is a commonplace experience in practices that held on to archives from the 1990s. If you still have thermal faxes in your boxes, they are dying as you read this sentence.
The evidence is separate from the document. The fax itself carries no record of its own transmission. It is the report (or the confirmation email, in fax-to-email) that attests to the date, time, number and page count. Archiving one without the other means keeping only half of what matters.
The header is fragile. The header line printed at the top of every page — sender's number, date, pagination — is what makes a fax recognisable as such. A sloppy scan that crops the first centimetre of the page removes that line, and with it much of the document's evidential value.
How long should you keep a fax?
The question is badly framed, but everyone asks it. The retention period does not depend on the channel used: it depends on the nature of the document. A purchase order sent by fax must be kept for exactly as long as the same purchase order sent by email or post. The fax is merely a means of transport.
The usual retention periods in France, as set out on the entreprendre.service-public.fr portal and in the CNIL's recommendations on storage limitation:
| Type of document transmitted | Retention period | Starting point |
|---|---|---|
| Customer or supplier invoice | 10 years | End of the financial year |
| Accounting record, book and register | 10 years | End of the financial year |
| Commercial contract, correspondence | 5 years | End of the contract |
| Payslip (employer's copy) | 5 years | Issue |
| Tax return and supporting document | 6 years | Last transaction |
| Medical record in a healthcare facility | 20 years | Last visit |
| Public procurement (tender file documents) | 5 to 10 years | End of performance |
| Follow-up, unsigned quote, prospecting | 3 years maximum | Last contact |
Two symmetrical pitfalls.
The first is throwing away too much. An agreement obtained by fax in 2021 and deleted in 2023 "because it was old" will leave you unarmed in a dispute arising five years later.
The second, more frequent and more costly, is keeping everything indefinitely. The GDPR requires a limited and proportionate retention period: a fax repository containing health data or customer contact details kept "just in case", with no defined end date, is a clear-cut case of non-compliance, compounded by the risk in the event of a breach. We covered this point in detail in our article on fax and the GDPR: archiving logic is its direct extension.
Working rule: one retention period per document category, written down in black and white in a table, and an annual purge. No "forever" periods unless there is an explicit legal obligation.
What exactly should you archive?
For every fax that matters, a minimum file of three items.
1. The document received or sent
Every page, in order, with the headers visible, including the cover sheet. A cover sheet is not an accessory: it carries the subject, the sender, the recipient and the stated page count — it is what allows you to detect, years later, that a page is missing. If you haven't yet standardised yours, our cover sheet template also doubles as an archiving record.
2. The transmission report or delivery confirmation
With fax-to-email, this is the confirmation email: keep it with its technical headers (Received:, server timestamps), which make it far more than a screenshot. When exporting, a simple .eml or a PDF of the full email is enough; the important thing is not to settle for the message body retyped by hand.
3. The record from the transmission log
Most online fax services keep a searchable log of sent and received items, exportable as CSV. Exporting it once a quarter is a safety belt: if a confirmation email vanishes, the log remains. Careful, though: these logs often have a limited retention period on the provider's side (six months, a year). The archive is yours, not theirs.
Formats: PDF/A rather than "plain PDF"
A fax received via fax-to-email generally arrives as a PDF or a TIFF. Both are fine, but for long-term archiving, two points are worth making.
PDF/A is the standardised flavour of PDF designed for archiving (ISO 19005). It prohibits everything that makes a PDF unreadable over time: non-embedded fonts, dynamic content, encryption. Most office tools offer a "PDF/A-2b" export behind a single checkbox. Get into the habit.
Multipage TIFF remains the historical fax format: lossless, one file per fax, very widely readable. It is an excellent preservation format, though less convenient to consult.
What to avoid:
- JPEG for text: compression creates artefacts around characters, automatic reading becomes poor, and a second-generation copy is decidedly degraded;
- screenshots of documents;
- the proprietary formats of a management application that you may no longer own in eight years' time.
Think about the text layer too. A fax is an image: without optical character recognition, it is invisible to search. Running OCR at the archiving stage — most scanning solutions offer it — turns a pile of mute files into a searchable database. On a poor-quality fax, OCR will sometimes fail; all the more reason to take care over reception, as explained in our guide to illegible faxes.
Dealing with the past: digitising paper faxes
If you inherit boxes of faxes, the digitisation campaign needs planning.
Start by sorting before scanning. Scanning ten thousand pages of which nine thousand are past their retention period wastes time twice over: at capture, then at search. Sorting by year and by category, even roughly, halves the work — and more.
On the hardware side, a duplex scanner with an automatic document feeder changes everything: we're talking dozens of pages a minute versus one every fifteen seconds on a flatbed. Set the resolution to 300 dpi in greyscale — there is no point going higher for a fax, whose native resolution tops out at around 200 × 200 dots per inch. A good paper guillotine is only useful if you are willing to unstaple and cut up the bundles, which is rarely desirable for documents with evidential value.
For thermal faxes that have already faded, a scanner with manual contrast adjustment often rescues what looked lost: increase the contrast, switch to pure black and white, accept a little noise. And store the remaining originals in acid-free archival sleeves, away from light, until the project is finished.
Naming, filing, finding
This is where everything is won. Successful archiving is recognisable by one thing: any colleague can find any fax in under two minutes, without calling you.
A naming convention that has proved its worth:
2026-03-14_recu_0033145xxxxx_MARTIN-SA_mise-en-demeure_3p.pdf
2026-03-14_recu_0033145xxxxx_MARTIN-SA_mise-en-demeure_RAPPORT.pdf
In order: ISO date (automatic chronological sorting), direction (recu / envoye), the correspondent's number, the third party's name, the subject in kebab-case, the page count. The report takes the same name with a suffix — the two files stay side by side whatever the sort order.
The folder tree, for its part, should be boring:
/Fax/2026/03/ → documents for the month
/Fax/_journaux/2026-T1.csv → quarterly export
No "Miscellaneous" folder, no folder named after an employee who left two years ago. And above all, a single reference location: the worst situation remains the one where the fax exists in five versions in five different email inboxes, with nobody knowing which one is authoritative.
Backing up: the 3-2-1 rule applied to faxes
ANSSI and CERT-FR restate it with every wave of ransomware, and it applies to your fax archives just as it does to everything else:
- 3 copies of the data,
- on 2 different types of media,
- with 1 off-site or offline.
In practical terms for a small business or a professional practice: the working folder on the company server or cloud, a copy on an encrypted external hard drive stored somewhere other than the office, and a rotation. For larger volumes or ten-year retention, a two-bay NAS in mirror mode offers a good compromise between cost and peace of mind — provided you understand that a mirror is not a backup: it protects against a disk failure, not against malicious encryption or accidental deletion.
Two practices that almost nobody follows, and that separate a real archive from wishful thinking:
- Test the restore once a year. Pick three files at random from the 2022 archive and open them. That's all. You will sometimes be surprised.
- Log access to archives containing sensitive data. A folder of medical or legal faxes accessible to all staff is an incident waiting to happen.
If your archives contain health data, remember that hosting them falls under HDS certification (health data hosting provider) as required by the French public health code: a hard drive in a drawer does not tick that box.
When to destroy, and how
End of life is part of archiving. Once the retention period has passed, deletion is not optional: it is the very principle of storage limitation.
For paper: a cross-cut shredder, level P-4 at minimum under the DIN 66399 standard, is the sensible standard for business documents; strip cuts are far too easy to reassemble. For large volumes, a destruction service with a certificate is more economical and provides a record.
For digital files: moving items to the recycle bin is not enough on a disk that will be reused or resold. Use secure erasure, or physically destroy the medium for sensitive data. And don't forget the internal memory of fax machines and multifunction devices: they often retain the most recent documents processed. We discuss this point in our article on decommissioning a fax machine.
Keep a disposal record: date, document category, period covered, method, person responsible. One line per campaign, in a spreadsheet. That document is what will prove you did not lose a record, but applied a policy.
Frequently asked questions
Does a fax archived as a PDF have the same value as the paper original?
Under French law, a reliable copy of a written document has the same evidential force as the original (Article 1379 of the Civil Code), provided that the reproduction process guarantees integrity and durability. A faithful, unaltered scan, kept together with its transmission record, is therefore perfectly admissible. A timestamp or a digital hash strengthens the case further. We go into detail in our article on the legal value of fax.
Should you keep paper originals after scanning?
For most commercial documents, no, provided the scan meets the conditions for a reliable copy. For high-stakes items — deeds, handwritten undertakings, ongoing litigation files — keep the original until the dispute is resolved. Doubt costs less than a box of archives.
How long does my online fax provider keep my documents?
It depends on the service, and it is rarely long: a few months to a few years. Never confuse a provider's retention with your archive. Read the stated period, export regularly, and check what happens when the account is closed. Our FAQ page answers this point for MondialFax.
How do you archive faxes received from abroad?
Exactly the same way, adding the full number in international format to the file name. That is what will allow you, two years later, to identify a correspondent nobody remembers. The list of supported countries remains useful for piecing together a doubtful dialling code.
Is an email enough as an archive?
An email inbox is a flow, not an archive: quotas, deletions, staff departures, no naming convention. Receiving your faxes by email is excellent — that is the whole point of fax-to-email — but the next step is to extract the documents into a dedicated folder tree.
Key takeaways
- The retention period depends on the document, not the fax: 10 years for accounting, 5 years for contractual matters, 3 years for prospecting.
- Always archive the document + transmission report pair, never one without the other.
- Prefer PDF/A or multipage TIFF, with an OCR layer so you can search.
- Thermal faxes fade: digitise them now, at 300 dpi in greyscale.
- A
date_direction_number_thirdparty_subjectnaming convention and a folder tree by year are enough to keep the archive alive. - Apply the 3-2-1 rule and test the restore once a year.
- Schedule destruction: annual purge, P-4 cross-cut for paper, backed by a disposal record.
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