Number Range 400 for Sales Calls: an Operator’s Guide (BOE 2026)

In an earlier article we explained what the 400 prefix for commercial calls is and why it affects any user who receives this type of call. This second installment is aimed at operators’ technical teams: who allocates the numbering, which deadlines are mandatory, what characteristics the range has, and what exactly counts as a “commercial call.”

Before getting into the details, one clarification about the regulatory status: the SETID’s Resolution of April 14, 2026 (BOE no. 93, of April 16) is final text in force since April 17, 2026, not a draft or a proposal still open for comments. The public hearing for affected sectors and the CNMC’s mandatory report were both completed before publication. What remains open is the six-month adaptation period, ending around October 17, 2026, and a judicial appeal filed by the AEERC against the measure, which has not, for now, suspended its application.

Where does it come from, and what does it look like on the inside?

The obligation stems from Article 16.3 of Law 10/2025, of December 26, on customer service, which requires commercial calls to be distinguished from customer-service calls using a specific code. The SETID implements that obligation by assigning the NXY=400 segment of the National Numbering Plan; the CNMC manages and assigns the numbering by operator, just as it does for the other ranges.

These are nine-digit national numbers that are outbound-only: if a user tries to call back, the call simply won’t connect, so operators must actively block inbound traffic to the range. For interconnection purposes they’re treated as fixed-network numbering, and they may only route to end-user numbers (geographic, mobile, or nomadic), never to PBXs or SIP trunks.

The number itself takes the form 400XXXYYY, where the third block of digits (XXX) identifies the operator responsible for managing that numbering and the YYY block identifies the associated telemarketing company (and a company can have as many numbers as it wants). It’s important to understand, though, that each operator responsible for a numbering block has its own prefix, some operators hold several prefixes, typically the ones that place the most telemarketing calls and have the greatest numbering needs.

Who allocates the numbering, and the deadlines

The CNMC assigns numbers to operators registered in the Operators’ Registry, not directly to telemarketing companies: if an operator provides service to a financial institution or a contact center, it’s that client company that requests numbering through the operator. The adaptation period ends six months after entry into force (October 17, 2026); from that date on, using any other range for commercial calls becomes an infraction.

A lesser-known detail is that the 400 range comes with number portability attached. In its preliminary report (INF/DTSA/027/26), the CNMC itself proposed placing the range within special-rate numbering, the same family as 900, 901 or 902, precisely so that number portability would apply automatically. That’s a striking choice, because since it’s an outbound-only range, the usual reason for porting a number, staying reachable on the same number after switching operator, simply doesn’t apply. The most plausible explanation is that portability here benefits the company using the 400 number as the caller ID: it lets them switch operator or contact-center provider without losing a number that’s already registered in anti-spam apps, customer address books, or their own campaigns.

One thing is still pending: as of today, the 400 range doesn’t appear in the CNMC’s public numbering lookup tool (numeracionyoperadores.cnmc.es), where you can otherwise check the allocation of geographic, mobile, or special-rate blocks. Until the CNMC updates that database, the reliable reference for which operator holds each 400 block remains the allocation notice itself, not the lookup tool.

Who must use it, and what counts as a “commercial call”

The obligation falls on companies within the scope of Law 10/2025 (basic services of general interest, or companies and groups with more than 250 employees, €50 million in revenue, or €43 million on the balance sheet) and, more broadly, on communications that telecommunications regulation (Article 66.1 of Law 11/2022) defines as “calls for commercial communication purposes”: those that promote, directly or indirectly, the goods or services of anyone carrying out a commercial, industrial, or professional activity.

Given that definition, it’s worth clarifying two common cases. An NGO calling to recruit members or ask for a donation doesn’t, in principle, fall into this category: it isn’t selling goods or services for a price, and Law 10/2025 itself sets out a separate, more flexible regime for non-profit entities, one that’s still pending regulatory development. Even so, a gray area appears when the NGO outsources to a contact center that also runs commercial campaigns for other clients, a scenario worth assessing case by case.

A voting-intention poll ahead of an election doesn’t count as a commercial call either: it doesn’t promote goods or services tied to an economic activity, so it falls outside the scope of Law 10/2025 and of this resolution. Political parties and polling companies are governed by their own electoral and data-protection rules, not by the 400 range.

As a general rule of thumb for operators: if the client’s communication is selling something for a price, it belongs on the 400 range; if it’s limited to informing, surveying, or requesting a signature or donation with no commercial consideration involved, it calls for a specific analysis, though on the face of it, it shouldn’t be assigned to this range.

The technical checklist

In summary, the steps an operator needs to take are: open up the 400 range in the network, in SIP signaling, and in billing, treating it as fixed numbering for interconnection purposes; block any inbound call directed at a 400 number; request numbering from the CNMC during the initial assignment period if serving commercial campaigns; update the CRMs, dialers, and dial plans of telemarketing clients so the outbound CLI matches the 400 range; and put in place mechanisms to detect irregular traffic (numbering without a specific code, or spoofed numbering), as required by Article 16.4 of Law 10/2025, a point the CNMC is going to be watching closely.

Will this reduce phone spam?

Having reviewed the resolution and Law 10/2025, it’s worth tempering expectations: the 400 range isn’t an anti-spam measure, it’s a labeling measure. It will let users and call-blocking apps identify at a glance that a call has advertising purposes, but it won’t by itself reduce the volume of commercial calls being made; companies will keep calling just as much, only now identifiably. The real anti-spam effect will come if users and operators can block the entire range with a single filter, something that’s been impossible until now because it was mixed in with ordinary numbering. In that sense, a meaningful impact is worth expecting, though not necessarily the one usually associated with this measure.