The area code 04 historically designates the telephone zone of the South-East of France. Within this zone, the following two digits help to refine the geographical location of the call. A number starting with 04 12 thus refers to a specific sub-zone, linked to departments in the Auvergne-Rhône-Alpes region.
Authentication of landline calls: what has changed for numbers starting with 04
Since 2024, Arcep has made the authentication of landline phone numbers in France effective. This mechanism requires operators to verify that the number displayed during a call corresponds to that of the actual caller. A non-compliant call can be blocked or masked even before reaching the recipient.
This measure directly affects geographical numbers such as those starting with 04 12. Previously, telemarketing platforms could display a phone number with the area code 04 12 in France without having any real link to the concerned area. Authentication makes this impersonation technically detectable by operators.
Since January 1, 2026, this obligation also extends to mobile numbers. The regulatory framework now covers the entire French numbering plan, which enhances the reliability of identifying an incoming call, whether it comes from a landline or a mobile.
French numbering plan: how to read a number in 04 12
The French telephone numbering system divides the metropolitan territory into five zones, each associated with a two-digit area code. 01 covers Île-de-France, 02 the North-West, 03 the North-East, 04 the South-East, and 05 the South-West.
Within the 04 zone, the following two digits (here, 12) specify the departmental or local prefix. This prefix is assigned by Arcep to operators serving a given territory. A number in 04 12 points to municipalities located within the Auvergne-Rhône-Alpes perimeter, linked to the departments covered by this range of numbers.
Complete structure of a French landline number
- The first two digits (04) identify the large geographical area, here the South-East of France
- The next two digits (12) designate the local prefix assigned to an operator for a specific territory
- The last six digits form the actual subscriber number, unique for each line
A number in 04 12 can be assigned to a company located outside the South-East, for example via a virtual switchboard.
Area code 04 12 and telemarketing: distinguishing a local call from a commercial call
Receiving a call from a number starting with 04 does not guarantee that it is a local correspondent. Some ranges of geographical numbers are used by telemarketing platforms that intentionally display a regional code to increase the pick-up rate. This practice, known as “local presence dialing,” exploits the trust associated with landline numbers.
French regulations have significantly tightened the conditions for using geographical numbers for prospecting purposes. Telemarketing is now prohibited outside regulated time slots, and non-authenticated calls can be cut off upstream by the recipient’s operator.
How to react to a suspicious call in 04 12
A single call without a voicemail is often a sign of automated telemarketing. Numbers reported multiple times by users are listed on reverse directories and reporting platforms.
- Check the number on a reverse directory before calling back, especially if no message was left
- Report abusive calls on the Bloctel platform or via 33 700 for unwanted SMS
- Activate call filtering offered by most operators, which relies on lists of authenticated numbers
Virtual landline number in 04 12: professional use and portability
Cloud telephony operators offer virtual landline numbers with the area code of their choice, including 04. A company based in Lille can thus have a number in 04 12 to display a local presence in the South-East, without having a physical office there.
The virtual number operates via Voice over IP and redirects calls to a landline, a mobile, or software installed on a computer. This flexibility explains why the correspondence between geographical area code and actual location of the business has become approximate.
Number portability remains guaranteed: a professional who changes operators retains their number in 04 12 without interruption of service. This right, regulated by Arcep, applies to both physical and virtual lines.
Difference between area code 04 and prefix 09
Numbers starting with 09, often assigned with triple-play Internet subscriptions, are not geographical. Unlike 04 12, a number starting with 09 provides no indication of the subscriber’s location. For a company wishing to anchor its image in a region of the South-East, a number in 04 remains a territorial marker recognized by customers.
A call in 04 continues to spontaneously evoke Lyon, Marseille, Grenoble, or Nice. This association remains a trust lever for companies targeting customers in these territories, provided that the number is properly authenticated with the operator.
