Faxing the CPAM, MDPH or CAF: a practical guide

Short answer: the French social administration has shifted its public-facing flows to online accounts — compte ameli, caf.fr, the URSSAF portal — but the fax has not disappeared for all that. It survives wherever the online service makes no provision: the medical department of a local health insurance fund asking for an extra document, a departmental MDPH still publishing a fax number on its reception form, a benefits department that must receive a supporting document before a two-month appeal deadline runs out. In those cases the fax has a single asset, but it is decisive: the time-stamped transmission report, which attests that a communication took place on a given day at a given hour with the equipment reachable at the number dialled. It is not a postal acknowledgement of receipt, it is not an electronic signature, and it never replaces filing through the online service where that is mandatory. But when you are facing a time bar, it is often the only document that saves a case. Three rules: check the number at source on the day itself, never fax a complete file when an online service exists, and keep the report together with an exact copy of the pages sent.

Why a social security body still publishes a fax number

One misunderstanding needs clearing up. The fax was not "forgotten" by the funds: it performs a function the web portal does not.

The online service is a closed tunnel. A compte ameli accepts the documents its form provides for, in the format and category it provides for. As soon as the request falls outside that frame — a document requested by a medical adviser, an employer's certificate in an unusual format, an additional expert report, a letter from an unaffiliated third party — the form has no box for it. The fax, by contrast, carries any page at all to any department that publishes a number.

The medical department is ring-fenced. The Assurance Maladie's medical department (the local medical service unit, or ELSM) handles health data and operates, for reasons of medical confidentiality, in a circuit separate from the administrative department. Historically that separation translated into dedicated fax lines, distinct from the reception desk's. Many practitioners still use this channel to send the additional items requested during a sick-leave check or a prior-agreement request.

MDPH offices are departmental. Created by the Act of 11 February 2005, the departmental centres for disabled people are run by the departmental councils. Their level of equipment varies widely from one department to another: some have a full online service, others still publish a fax number next to the postal address on their contact page. This is particularly true for exchanges with institutions, support services and multidisciplinary teams.

Finally, deadlines govern everything. In social security matters, appeal deadlines are short and unforgiving: two months to refer a case to the commission de recours amiable (CRA) after a decision is notified, then a further two months to bring the matter before the social division of the judicial court. When three days are left, registered mail that takes forty-eight hours to arrive and a platform returning an error are not reassuring options. A fax goes out in two minutes and produces an immediate trace.

What a fax proves before a fund — and what it does not

This is the part that matters, because everything else follows from it.

A transmission report establishes that a fax telephone communication was completed, on a precise date and at a precise time, with a device reachable at the number dialled, and that n pages were negotiated and then acknowledged under the ITU's T.30 protocol. It is a technical fact produced by a machine with no stake in the dispute.

What it does not establish:

• that the content received matches exactly what was sent — the report counts pages, it does not certify their text;
• that an officer read it or that the file was registered;
• that the number dialled is indeed that of the competent department, unless you can otherwise show where you got it.

In law, the fax amounts to a commencement of proof in writing within the meaning of article 1362 of the Civil Code: it must be corroborated by other evidence. That classification is very often enough in social security litigation, because the judge there freely assesses the evidence of filing within the deadline. A transmission report dated the last usable day, accompanied by a copy of the pages and a screenshot of the page where the number appeared, makes for a solid body of evidence.

The habit that changes everything: on the day you send, take a time-stamped screenshot of the official page where the number is published. Six months later the page will have changed and no one will be able to verify that the number ever existed.

Where the fax is still useful, department by department

The table reads simply: when an online service exists and covers your request, use it. The fax is not a channel of convenience, it is a backup or supplementary channel. Using it instead of a mandatory filing risks having the file treated as never received.

The seven-point protocol before hitting "send"

1. Check the number at source, on the day itself

Never a number found on a forum, never a number copied from a 2019 letter. Acceptable sources: the body's official site (ameli.fr, caf.fr, the departmental council's site for an MDPH), or the notification letter you are contesting, which almost always states the department and its contact details.

2. Draft a cover sheet that serves as a transmittal slip

It must carry: your social security or claimant number, the file reference exactly as it appears on the notification, the subject in one line, the total number of pages including the cover sheet, and your telephone number. A fund receiving ten metres of faxes a day gives priority to what it can identify in three seconds.

3. Scan cleanly

Fax transmission degrades. A faint stamp, a pencil signature, a photocopy of a photocopy become illegible. Use a duplex document scanner rather than a smartphone photo: straightened pages, in high-contrast black and white at 300 dpi, come through fax compression far better.

4. Number the pages by hand

"3/8" in the top right-hand corner of each sheet. If the department receives six pages out of eight, it will know which are missing and you will be able to prove it. One minute of work that saves a week of chasing.

5. Send during business hours

A transmission at 2 p.m. on a Tuesday stands a better chance of getting through than one at 11 p.m. on a Sunday, when a saturated line or a gateway under maintenance returns a silent failure. If the deadline allows, leave yourself a twenty-four-hour margin to try again.

6. Retrieve the transmission report

With an online fax service it arrives by email marked "success", with the time, the duration and the page count. With a physical machine, print it immediately — thermal rolls fade, and a monochrome laser printer will spare you the discovery of a blank page two years on. Our detailed advice on retention is in our guide to archiving your faxes and preserving their evidential value.

7. Build the three-part evidence set

Three items, stapled together or gathered in a single PDF: the transmission report, the exact copy of the pages sent (cover sheet included), and proof of where the number came from. Without the second, you prove a fax went out, not what it contained.

The special case of health data

An MDPH file contains a medical certificate. A prior-agreement request contains a diagnosis. A contested sick leave contains clinical details. These are health data within the meaning of article 9 of the GDPR, subject to a reinforced regime.

Three precautions are essential.

Separate the administrative from the medical. The medical section of an MDPH file is intended for the multidisciplinary team, not the reception desk. Send it under separate cover, or through the channel the form indicates. Faxing a certificate to a switchboard's general line is like leaving it in a shared tray.

Prefer secure health messaging if you are a professional. Since the rollout of the MSSanté scheme run by the Agence du Numérique en Santé, a doctor, a pharmacist or a healthcare institution has a compliant, traced channel. The fax remains a fallback when the recipient has no active MSSanté address. We set out these trade-offs in our article on medical faxing and health data.

Secure the sending workstation. A social security file scanned and then forgotten in the "Downloads" folder of a shared computer is a leak waiting to happen. An encrypted external hard drive for archiving and a cross-cut shredder for paper drafts cost less than an incident you have to report to the CNIL.

Three real-world scenarios

The forty-eight-hour time bar. You receive a refusal of daily sickness benefits dated the 10th, received on the 15th. The internal appeal period runs from notification. You draft your letter to the CRA over the last usable weekend: send it by registered post and fax it on Monday morning. The registered letter proves despatch, the fax proves the time of arrival. Total cost: a few euros.

The incomplete MDPH file. The MDPH asks for a document within a month, failing which the request will be closed without action. The departmental online service does not accept the format. The fax, with the file reference on the cover sheet, settles it in ten minutes — and the transmission report protects you if the document goes astray inside the internal circuit.

The healthcare professional and the prior agreement. A physiotherapist has to send a prior-agreement request with the prescription. The fund's medical department publishes a dedicated number. The fax is sent, the report filed in the patient record, and the start date of the fifteen-day period at the end of which agreement is deemed granted becomes enforceable.

Frequently asked questions

Is a fax as good as a registered letter with acknowledgement of receipt?

No. Registered mail with acknowledgement produces proof of despatch and of receipt, with legal value recognised by article 1369 of the Civil Code and, for its electronic version, by the eIDAS regulation. A fax produces proof of transmission that remains a commencement of proof in writing. Best practice as soon as anything real is at stake: send both on the same day.

Can a complete AAH application be filed by fax?

It is not advisable, and many MDPH offices refuse it. The Cerfa application form, the medical certificate and the supporting documents make for a substantial volume, often illegible after fax transmission. Use the departmental online service or postal mail, and keep the fax for one-off additions.

How do I know whether the fund has actually registered my fax?

The transmission report does not tell you. Call the department back two to three working days after sending, and note the name of the person you spoke to, the date and the time of the call in a spiral-bound tracking notebook kept with the file. This kind of personal running log has already carried weight in disputes.

Do I need a physical fax machine?

No. An online fax service is enough: you send from a computer or a smartphone, and the report arrives by email in PDF format, easier to archive than a thermal slip. The criteria for choosing a provider are set out in our comparison of the 10 criteria for choosing your provider, and the sending conditions are on our FAQ page.

What should I do if the fax fails every time?

Three causes dominate: the number is no longer allocated, the line has been migrated to VoIP without a working fax gateway, or the volume exceeds the receiver's memory capacity. Cut the send down to five pages, try again during off-peak hours, then switch to registered mail while keeping the failure reports: they prove your diligence.

In summary

• Online services first. Compte ameli, caf.fr, the URSSAF area, the MDPH online service: when the official channel covers your request, it takes precedence.
• The fax as backup or supplement, for whatever falls outside the form, for the medical department, and above all when a two-month appeal deadline is about to expire.
• The number is checked at source on the day itself, backed by a time-stamped screenshot.
• The cover sheet serves as a transmittal slip: NIR or claimant number, file reference, subject, page count, telephone.
• The three-part evidence set — transmission report + exact copy of the pages + origin of the number — makes the difference before an internal appeals commission.
• Health data is handled separately: medical section apart, MSSanté where available, secured sending workstation.
• Back it up with registered mail as soon as the contested decision has a lasting financial impact.