Fax and Building Permits: Deadlines Not to Miss

Short answer: an application for a building permit (permis de construire), a prior declaration (déclaration préalable) or a development permit (permis d'aménager) cannot be filed by fax. Filing is done through the municipality's single digital portal (guichet unique numérique) — mandatory since 1 January 2022 for municipalities with more than 3,500 inhabitants, article L. 423-3 of the code de l'urbanisme (Planning Code) — by registered post, or at the town hall counter against a receipt. On the other hand, as soon as the file is registered and numbered (the familiar PC 0XX XXX XX XXXXX), the fax becomes useful again: getting a supplementary document requested by the processing department, a certificate, a reply to the architecte des Bâtiments de France (Architect of French Historic Buildings), a withdrawal of application or an extension request to arrive the same day. Golden rule: you fax a document into an already numbered file, never the initial filing, and you duplicate it the same day through the official channel (digital portal or registered post).

Why planning law is the land of hard deadlines

The processing of a planning authorisation works the opposite way round from most administrative procedures: here, silence means consent. If the town hall does not reply within the processing period, the applicant obtains a tacit decision (article R. 424-1 of the Planning Code). That is a valuable protection… but it has a formidable flip side: the clock only runs if the file is complete, and a single missing document can throw off the entire timetable.

The basic time limits, set by article R. 423-23, are well known:

These periods are extended in a long list of cases: consultation of the Architect of French Historic Buildings in a remarkable heritage site or near a listed monument, opinion of a safety or accessibility commission for a building open to the public, a file subject to environmental assessment, a water catchment protection perimeter, an easement under a risk prevention plan. The processing department must notify this extension within the first month following the filing, by letter or electronically.

Above all, article R. 423-38 gives the administration one month from the filing date to request missing documents. The applicant then has three months to produce them. After that deadline, the application is subject to a tacit refusal (article R. 423-39). That is precisely where the question of the transmission channel becomes critical.

What a fax can do, and what it cannot

Transmissions that make no sense by fax

• The initial filing. Forms Cerfa 13406 (building permit for a single-family house), 13409 (other constructions) and 13703 (prior declaration) require scale drawings, a site plan dimensioned in all three dimensions, a graphic integration document and photographs. A fax crushes grey levels and loses the scale: the file would automatically be declared incomplete.
• Heavy graphic documents. A 1:100 section drawing or a 1:200 site plan sent by fax becomes unreadable. Dimensions vanish, easement hatching fills in solid black.
• Documents required in original form. Certificate of compliance with thermal and environmental regulations (RE 2020), earthquake-resistance certificate, original consent of the condominium association, notarised sale agreement.
• Litigation appeals. An appeal against a permit is brought before the administrative court (tribunal administratif), and whether a fax is admissible there is a special question: we covered it in our article on faxing the administrative court in the age of Télérecours.

Transmissions where a fax saves a deadline

• A simple administrative document requested by the processing department: insurance certificate, proof of ownership, extrait K-bis (company registration extract), bank details, power of representation, letter appointing an agent.
• The reply to a request for clarification from the case officer or the Architect of French Historic Buildings about a material, a joinery colour, a type of roof tile.
• A request to extend the validity of an authorisation (article R. 424-21: the request must be sent at least two months before the three-year validity period expires).
• The withdrawal of an application before a decision, or the transfer of a permit to a new holder when the notary is pressing.
• The declaration of works commencement (déclaration d'ouverture de chantier, DOC, Cerfa 13407) and the declaration of completion and compliance of works (déclaration attestant l'achèvement et la conformité des travaux, DAACT, Cerfa 13408), for which the town hall has three months — five in certain cases — to challenge compliance.
• An urgent correction notice: clerical error on the decision, misspelled name, wrong land registry reference, incorrectly reported floor area.

What a fax really brings to planning matters is a certain date of dispatch on a transmission report, in a field where one day's delay turns a consent into a tacit refusal.

The three departments to tell apart

Many applicants fax the wrong place because they confuse the players involved.

1. The municipality's planning department. It is the competent authority for issuing the authorisation in the vast majority of cases. In municipalities without a planning document, it is the prefect. The municipal planning department registers the file, issues the receipt, displays the filing notice and notifies the decision. Small municipalities often keep a fax machine in the general secretariat, shared with the registry office — our article on faxing the town hall, planning and civil registry explains how this works.

2. The shared processing department. Many municipalities delegate technical processing to their community of municipalities, to a conurbation authority or, by agreement, to the departmental directorate for territories (direction départementale des territoires, DDT or DDTM). It is this department that sends out the request for missing documents, and it is often this one you should fax, with a copy to the town hall. The request letter almost always bears the address and fax number of that department: read it rather than hunting for a number online.

3. The departmental unit for architecture and heritage (UDAP). This is the Ministry of Culture department where the Architect of French Historic Buildings sits. It is consulted whenever the project lies near a listed monument, in a remarkable heritage site or in a classified site. UDAP offices still work largely on paper and several keep an active fax line. Be careful: the ABF issues an opinion to the competent authority, it does not process your file. Every exchange with it must be copied to the processing department, otherwise your document will never make it into the administrative file.

To check that a number is not a dead line, the method is the same as for any public body: the official source first, the letter you received next, a verification call last. Our guide on checking a public administration fax number describes the procedure, and the directory of official numbers lets you cross-check.

The method in six steps

1. Reread the request for missing documents

It follows a standard format. It states the file number, the filing date, the precise list of missing documents with their Cerfa reference (PC2, PC4, DP6…), the three-month deadline and the recipient department. Never fax "the whole file": send exactly the documents listed, in the order listed, with their reference written at the top of each page.

2. Build a PDF that survives the fax

A fax transmits in black and white, at roughly 200 dots per inch. A grey photocopy or a poor-quality scan arrives unreadable. The right habits: scan in high-contrast black and white, 300 dpi, strict A4 format, text at 11 points minimum. A portable sheet-fed document scanner produces a far cleaner result than a hand-held phone photo, and for stamped certificates the difference is immediate. If you cannot scan, a smartphone tripod for overhead shots avoids shadows and keystone distortion. We detailed the settings in our article on preparing a PDF that stays readable after faxing, and the assemble a PDF file tool lets you merge documents in the right order.

3. Get the cover sheet right

In planning matters, the cover sheet does half the work, because the case officer receives dozens of pages a day with no idea which file they belong to. It must show:

• the full file number as it appears on the receipt;
• the date of the letter requesting documents and its reference;
• the applicant's name and the address of the land with its land registry references (section and plot number);
• the numbered list of documents sent and the total page count;
• the wording "envoi doublé ce jour par [guichet numérique / lettre recommandée n° …]" ("also sent today via [digital portal / registered letter no. …]").

The cover sheet generator produces this block in a minute.

4. Send and duplicate the same day

A fax gives a date of dispatch; it does not prove the document was read. The safe practice, in planning as elsewhere: fax for the date, then file on the municipality's digital portal or send a registered letter with acknowledgement of receipt the same day, with the same cover sheet. If you send a lot of registered mail during a building project, a registered mail tracking logbook stops you losing tracking numbers at the moment you need to produce them.

5. Archive the transmission report

The transmission report — number dialled, date, time, page count, the "OK" mention — is the only usable record. Keep it with the PDF you sent, in the same folder as the filing receipt and the decision. In planning matters the retention horizon is long: the ten-year structural warranty runs for ten years from acceptance of the works, and a third-party appeal or a compliance challenge can arise years later. An archive box for suspension files per project, or simply a large-format lever arch file for folded drawings, is enough to keep everything together. Our retention benchmarks are set out in the article on archiving transmission receipts.

6. Check that the document actually made it into the file

This is the step everyone forgets. Two or three working days after sending, call the processing department and ask for confirmation that the document has been registered. Note the officer's name, the date and the time. A fax that was sent but filed in the wrong tray is worth no more than a fax never sent.

Pitfalls specific to planning law

The three-month deadline cannot be extended. Unlike other procedures, the article R. 423-39 period for producing missing documents cannot be extended on request. Three months after notification, the refusal is tacitly acquired. A fax sent the day before the deadline, duplicated the same day, remains the safest rescue manoeuvre.

A late request for documents is unenforceable. If the town hall requests documents after the first month, that request does not interrupt the processing period (settled case law of the Conseil d'État (Council of State)). Check the date of the letter: it is sometimes worth more than a long exchange.

A document that is not required cannot be demanded. The list of documents to be attached is exhaustive (articles R. 431-4 et seq.). A processing department cannot require a document absent from that list in order to declare a file incomplete.

On-site display cannot be faxed. The regulatory sign determines the starting point of the third-party appeal period (two months from the first day of continuous display). Have it recorded — dated photographs, a neighbour's statement, a judicial commissioner's report — but do not count on a fax for that.

The digital portal remains the legal channel. Since 2022, municipalities with more than 3,500 inhabitants must offer an online procedure. A fax is never an alternative to filing: it is an occasional accelerator during processing.

If you have neither a fax nor access to the digital portal, the Maisons France Services (France Services centres) assist with these procedures free of charge: see our article on France Services help with faxing a file.

Frequently asked questions

Can a building permit application be filed by fax?

No. Filing is done through the municipality's single digital portal, by registered post or at the counter against a receipt. A file received by fax would be rejected as incomplete: scale drawings and photographs do not survive the transmission.

My planning department no longer has a fax — what should I do?

That is common in large conurbations, which have switched to their digital portal and a functional email address. In that case, upload the document to the portal, keep the filing timestamp and duplicate by registered post. The fax remains most useful for small municipalities and UDAP offices.

Does a fax stop the three-month clock for missing documents?

What counts is actual receipt of the document by the competent department within the deadline. A dated transmission report is serious prima facie evidence of dispatch, but it is not an acknowledgement of receipt. Hence the rule of duplicating the same day through a channel that produces proof of receipt.

Should I fax the town hall or the processing department?

The department that wrote to you, with a copy to the town hall. When processing is shared with a community of municipalities or the DDT, that department holds the technical file, but the town hall remains the authority that will sign the decision.

Does the Architect of French Historic Buildings accept documents by fax?

Several UDAP offices keep a fax machine in the secretariat and accept written clarifications or documented samples. But the ABF only issues an opinion: your transmission must also be copied to the processing department to enter the file.

What about the declaration of completion of works?

The DAACT (Cerfa 13408) is normally filed on the digital portal or by registered post. A fax can be used to make it arrive on a specific date — to line up a notary appointment, for example — provided you duplicate it, because that date starts the town hall's period for challenging compliance.

In summary

• Never file the initial application by fax: digital portal, registered post or filing against a receipt.
• Yes to a fax for a document in a numbered file: certificate, supporting document, reply to the case officer or the ABF, extension, withdrawal, DOC, DAACT.
• One month for the administration to request missing documents, three non-extendable months to produce them (articles R. 423-38 and R. 423-39).
• Identify the right department: town hall, shared processing department or DDT, UDAP for the heritage opinion — and always copy the processing department.
• A complete cover sheet: file number, land registry references, list of documents, page count, mention of the duplicate channel.
• High-contrast black and white PDF, A4, 300 dpi: a 1:200 plan has no place in a fax, a certificate does.
• Duplicate the same day through the digital portal or by registered post, and keep the transmission report for as long as the ten-year structural warranty runs.