Prefix 400 for commercial calls in Spain: requirements, deadlines and how it affects users and operators (BOE 2026)

We now have the BOE that intends to regulate commercial calls once and for all. It’s the Resolution of 14 April 2026, published in the Official State Gazette, which exclusively assigns the 400 prefix to commercial calls in Spain. In other words: if you’re fed up with answering the phone only to find a telephone operator, an energy supplier or a finance company offering you a loan you didn’t ask for, things change in 2026. From now on, when you see a number starting with 400, you’ll know beyond any doubt that there’s someone on the other end trying to sell you something. Let’s go through it calmly: when it comes into force, what real advantages it brings to you as a user, what benefits the operator gets, what drawbacks the measure has, and, most interestingly, why your telecom provider may actually want you to block all commercial calls at once.

What the BOE actually says about the 400 prefix

The resolution, published in BOE number 93 of 16 April 2026, develops Article 16.3 of Law 10/2025, of 26 December, on customer service. This means the Ministry for Digital Transformation and Civil Service has decided that the segment NXY = 400 (nine-digit national numbers starting with 400) is exclusively reserved for making commercial calls. The key points to keep in mind are these:

• The 400 range is exclusively outbound. You can’t call back a number starting with 400 because it doesn’t accept incoming calls. If you try to call, the connection won’t be established.
• No company will be allowed to make commercial calls from a range other than 400. No more receiving advertising from a geographic landline that looks like it’s from your city (commercial calls from mobile numbers were already banned last year).
• Operators are required to open the 400 range on their networks, route calls correctly and, in addition, inform their customers about the opening of the range between months 5 and 8 after the resolution comes into force.
• Calls from the 400 range are treated, for interconnection purposes, as originating from a fixed-network access.
• Operators must offer their customers, on request, the option to fully disconnect the reception of commercial calls from the 400 range.

When will the 400 prefix be mandatory?

The resolution came into force on 17 April 2026 (the day after its publication in the BOE), but it grants a period of 6 months for the whole ecosystem to adapt: the CNMC assigns the numbers, operators enable them on their networks, and the companies making commercial calls migrate their PBXs and dialers. Translated into the calendar: starting in October 2026, commercial calls can only be made from the 400 range. Any company that keeps calling from a 91x, 96x, 6xx or 7xx number to sell something will be in breach of the rule and will be exposed to penalties. The sixth section of the resolution says it quite clearly: “once that period has elapsed, commercial calls may only be made through the NXY = 400 range, and no other numbering range may be used from then on to make commercial calls“.

Advantages for the user: identifying before picking up

The most obvious advantage, and the one that gave rise to this measure, is that you’ll finally know what kind of call you’re receiving before picking up. Until now, a call centre could call you from any number (geographic, mobile, nomadic) and it was impossible to tell it apart from a call from your child’s school, the garage or your doctor. With the 400 prefix the rules are very simple:

• Clear and unambiguous identification: if the number starts with 400, it’s a commercial call. Period. You can decide whether or not it’s worth answering without a second thought.
• Total blocking option: the resolution requires operators to offer a disconnection service. Ask your provider to block the 400 range and forget about commercial calls forever, regardless of whether you’re on the Robinson List or not.
• Less fraud: scammers who did spoofing by impersonating geographic numbers lose a tool. A call starting with 400 cannot be fraudulent in the classic sense: if it’s not a legitimate company doing telemarketing, it shouldn’t be there.
• Traceability: filing a complaint with the AEPD is much easier when the range of origin is perfectly defined.

Advantages for operators

At first glance it might seem that operators lose out with this measure, but it’s not all negative. They have reasonable reasons to be happy:

• Less support workload: reducing ghost calls and complaints about phone spam directly eases the burden on customer service departments.
• Reputation boost: being able to offer “one-click commercial call blocking” is a great selling point for attracting and retaining customers.
• Greater control over their numbering: they stop seeing their mobile and geographic ranges get “burned” because of third-party campaigns that get them flagged as spam in collaborative lists.
• New revenue stream: the 400 is a new numbering resource that is assigned, managed and billed. Selling 400 numbering to companies, call centres and campaign issuers is an added business.
• Less international fraud: robocalls and spoofing lose effectiveness, and operators stop being the target of many regulatory complaints.

Drawbacks of the measure

It’s not all perfect, and it’s worth looking at the flip side as well:

• Adaptation cost: operators, virtual PBXs, call centre software vendors and campaign issuers have to tweak configurations, routing, default CLIs, outbound rules, CRMs, dialers and a long etcetera within six months.
• Risk of mass blocking: if everyone blocks the 400 range, legitimate companies (not all commercial calls are a scam: there are renewals, upselling to customers, useful notices) are left without a telephone channel. Some will migrate directly to WhatsApp, SMS or email, bringing the spam problems we already know on those channels.
• Flight to other channels: when one channel closes, telemarketing shifts. Get ready for more SMS, more RCS and more WhatsApp Business messages.
• Calls from abroad: the resolution is binding in Spain, but a call centre calling from outside Spain with international numbering is, in practical terms, out of the direct reach of the rule. Here we’ll still need to rely on the Robinson List and the AEPD.
• Usability issue: many older users don’t tell one prefix from another. The measure will need to be accompanied by good information.
• Initial confusion: during the first months, commercial calls from 400 numbers will coexist with calls from older numbering belonging to those who haven’t yet adapted.

Why your telecom provider wants you to block commercial calls

Here comes the part almost no one talks about. The resolution allows operators to offer their customers the option to disconnect the 400 range, and they’ll sell it as an advantage (and it is, for you). But there’s a second reading worth keeping in mind. Most of the commercial calls you receive have a very specific goal: to get you to switch providers. Telephone, electricity, gas, insurance, bank. They’re competitors of your operator (or companies allied with competitors) trying to win you over with a better deal. If your provider offers you one-click blocking of all those commercial calls, they’re doing two things at once:

1. They provide you with a useful service you’ll appreciate.
2. They shield their customer base. If competitors’ offers don’t reach you, it’s much less likely that you’ll consider switching to another operator.

Put another way: when your provider tells you “block commercial calls“, it’s protecting itself from the competition making you a better offer than its own. It’s legitimate, it’s legal, and it’s even an apparent win-win, but it’s worth being aware of.

Implications if you’re an operator or integrator

If you’re an operator, this measure forces you to:

• Open the 400 range on the operator’s network, on the PBX and in the SIP signalling. Route the range correctly and make sure calls destined to 400 are rejected.
• Request 400 numbering from the CNMC during the initial assignment period if you’re going to provide the service to campaign-issuing companies. The CNMC has foreseen exceptions to the order of submission in this initial phase, so it’s worth paying attention.
• Guarantee portability of 400 numbers between assignee operators.
• Adapt CRMs and dialers: change the CLI of outbound campaigns to dial from 400 rather than from geographic or mobile numbering.
• Clearly separate customer service and commercial calls. The 400 is only for commercial. It’s not valid for customer service, and it’s not valid for after-sales either.
• Implement the disconnection: end-user operators have to offer their customers the possibility of blocking the 400 range upon request.
• Review contracts and privacy policies with client companies so it’s clear from which range calls will be made and how consent is documented.
• Actively inform between month 5 and month 8 after the entry into force, as the BOE requires.

And take note: the CNMC is in charge of supervising all of this, so the temptation to “keep calling from a 91x because it converts better” is going to come at a high cost.

What future is there for the Robinson List?

At Sinologic we already talked about the Robinson List a few years ago, explaining that it’s a service companies have to filter their databases against before calling. The logical question is: with the 400 prefix and the possibility of total blocking, does it still make sense to keep the Robinson List? My opinion, after reading the rule calmly, is that the Robinson List doesn’t disappear, but its role changes:

• Blocking the 400 range is an “all or nothing” switch: either you receive commercial calls or you don’t receive any. The Robinson List is still useful if you want sector-based blocking (for example, nothing from energy or telecoms but yes from NGOs).
• The Robinson List also covers email, SMS and postal mail, channels that the 400 prefix doesn’t touch at all. And it’s precisely to those channels that part of telemarketing is going to shift.
• It’s still the legal basis for filing a complaint with the AEPD when a company calls someone who hasn’t given their consent, even if they call from a legitimate 400 number.
• And the issue with privacy policies is still in force: the day you accept “transferring your data to third parties for commercial purposes”, that company has permission to call you even if you’re on the Robinson List. That doesn’t change with the 400.

The 400 is one more layer, it doesn’t replace the Robinson List. The ideal is to combine them. Sign up for the Robinson List to cut off the tap by sectors and across all channels, and use 400 blocking as a quick and total reinforcement if you don’t want a single commercial call.

It’s one of those simple measures that should have arrived ten years ago. It’s not going to end phone spam overnight, but it brings order, lets you identify at a glance what kind of call you’re receiving, and, above all, gives you a real tool to say “no, thanks” without having to pick up.

If you’re a user, you know the drill: when your operator sends you the notice between months 5 and 8, decide whether you want to block commercial calls from 400, but don’t forget you’ll also be blocking offers from the competition. If you’re an operator or integrator, you have six months to get everything ready. And if you’re a company that runs campaigns, start requesting your 400 numbering from the CNMC and review your consents, because the era of opaque telemarketing is over.