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Help logging inIf you make commercial or customer-service calls to contacts in Spain, two rules affect which numbers you can call from:
- Orden TDF/149/2025 restricts mobile numbers for these calls, and applies to any business making them.
- BOE resolution of 14 April 2026 goes further for large companies and essential-service providers, introducing a dedicated prefix, 400, that becomes mandatory for commercial calls from 17 October 2026.
This article explains what these rules mean for you, what's already in force, what's coming, and which numbers to use when.
Which numbers to use, and when
| Numbering type | Before 17 October 2026 | From 17 October 2026 |
|---|---|---|
| Geographic (fixed, +34 9XX) | Allowed for commercial and customer-service calls | Allowed for customer-service calls only. Commercial calls must use prefix 400 |
| 800 / 900 | Allowed for commercial and customer-service calls | Allowed for customer-service calls only. Commercial calls must use prefix 400 |
| Mobile (+34 6XX / 7XX) | Not allowed for unsolicited commercial or customer-service calls. May still work if you have documented consent or an existing commercial relationship. Check with the customer's legal counsel. | Same restriction continues to apply |
| Prefix 400 | Not available | Mandatory for all commercial calls |
Mobile numbers can't be used for unsolicited commercial and customer service calls
Since 7 June 2025, Article 9 of Orden TDF/149/2025 bans mobile numbers (+34 6XX or +34 7XX) for unsolicited commercial calls and customer-service calls. This applies regardless of company size. As shown above, geographic and 800/900 numbers remain valid alternatives, thanks to Article 10 of the same order.
Important: If you use Aircall mobile numbers in Spain for outbound sales or support calls, check with your legal or compliance team whether those calls fall under this restriction.
Prefix 400: the new range for commercial calls
The Boe resolution of 14 April 2026 creates a new number range reserved for commercial calls only: numbers starting with 400, in the format +34 400 XXX XXX. Spain's Ministry for Digital Transformation announced the measure alongside the Resolution's publication.
This requirement applies to businesses covered by Law 10/2025, Spain's law on customer service standards, generally providers of essential services (like water, gas, electricity, and telecommunications) and large companies selling to consumers. The law includes transitional provisions and possible exceptions.
Tip: Check with your legal or compliance team whether your organisation falls within the scope of Law 10/2025, and whether any transitional exceptions apply to you, before deciding on your numbering strategy.
A few things to know about prefix 400 numbers:
- They're outbound only, so they can't receive incoming calls.
- They can't be used for customer service or anything other than commercial calls.
- For interconnection between carriers, they count as calls from a fixed line.
Important: Prefix 400 numbers can't receive calls. If a contact sees a missed call from a 400 number, they won't be able to call it back.
Note: Spanish telecom operators may let their own customers block all incoming calls from the 400 range by default. Some of your contacts may opt out of receiving these calls entirely.
Which calls need a prefix 400 number
From 17 October 2026, any call made for a commercial purpose needs to come from a 400 number, no matter your relationship with the contact or whether they've given consent.
| Call type | Requires prefix 400 | Why |
|---|---|---|
| Cold call to a prospect with no prior relationship | Yes | A commercial call in its clearest form |
| Follow-up to a lead who submitted a form | Yes | Still a commercial call, even with prior consent |
| Upsell or cross-sell to an existing customer | Yes | The purpose is to sell an additional product or service |
| Outbound campaign to your own contact database | Yes | Applies regardless of data quality or source |
| Customer service or post-sale support | No | Not a commercial call. Fixed, 800/900, or other permitted numbering can be used |
| Renewal, onboarding, or account check-in calls | Depends | Whether it counts as commercial depends on whether the call includes a sales component |
| Billing or collections calls | No | Not commercial in nature |
Note: Consent and numbering are two separate things. Having a contact's consent under GDPR determines whether you're allowed to call them, not which number you must call from.
Prefix 400 numbers with Aircall
Aircall provides Spanish numbering today, including geographic, mobile, and 800/900 numbers, through local numbering partners, and is extending this to prefix 400 numbers. For the current availability of prefix 400 numbers on your account, check your Aircall numbers page or contact Aircall support.
Best practices for compliant numbering
Steps
- Use geographic (+34 9XX) or 800/900 numbers for commercial calls before 17 October 2026, and prefix 400 numbers from that date.
- If you use mobile numbers for calls to contacts with prior consent, keep timestamped, auditable consent records for each contact.
- Check with your legal or compliance team whether Ley 10/2025 applies to your organisation and whether any transitional exceptions apply.
- Check your Aircall account or contact support to confirm prefix 400 availability before your commercial calling needs to migrate.
FAQs
Can I use fixed numbers for commercial calls?
Yes, before 17 October 2026. From that date, commercial calls need to come from prefix 400 numbers. Fixed numbers stay valid for customer-service calls at any time.
Does this rule apply to B2B calls, or only to consumers?
The rules don't draw a line between B2B and B2C calls. Whether a number restriction applies depends on whether the call is commercial in nature, not on who the recipient is. Check your specific use case with legal counsel.
What happens if a contact tries to call back a missed call from a 400 number?
They won't be able to. Prefix 400 numbers are outbound only and can't receive incoming calls.
What are the penalties for not complying?
Article 107.19 of Spain's General Telecommunications Law classifies non-compliance with numbering rules as a serious infraction, with fines ranging from €50,000 to €2,000,000 depending on the circumstances of the case.
Will I need to change phone providers to get a prefix 400 number?
No. Aircall will provide Spanish numbering soon (we are still working on it), including prefix 400, through local numbering partners. Contact your account team or Aircall support for the current availability in your account.
Does having a contact's consent mean I don't need to use a prefix 400 number?
No. Consent affects whether you're allowed to call someone under data protection rules. It doesn't exempt you from the numbering requirement. From 17 October 2026, commercial calls need to come from a prefix 400 number regardless of consent.