Over recent months, we have seen a growing number of UK taxpayers receiving letters from HMRC demanding payment of Spanish tax debts on behalf of the Agencia Estatal de Administración Tributaria (AEAT).
In many of these cases, the underlying issue is not the amount of tax assessed but a procedural flaw: the taxpayer was never properly notified in Spain. What may seem a technicality is, in reality, a serious breach of due process — one that can halt enforcement entirely.
Under Spanish administrative law, defective notification prevents an act from becoming legally effective. And under the rules of international tax cooperation, it also means that HMRC must suspend recovery once the taxpayer lodges an appeal in Spain challenging that notification.
The Supreme Court Reaffirms Notification Standards
In its Judgment 1221/2025 (Rec. 926/2024) of 1 October 2025 (ECLI: ES:TS:2025:4269), Spain’s Supreme Court reinforced a principle that has long underpinned administrative justice: a notification is valid only if the act being communicated is clearly identified.
The Court held that any attempt at notification must specify the date, content, and legal nature of the act — not simply an expediente or reference number. Vague or incomplete wording is insufficient.
Although the case arose in the context of an immigration procedure, its reasoning applies across all areas of Spanish administrative law, including tax. The message from the Supreme Court could not be clearer: notification is not a bureaucratic step, but a fundamental safeguard of the right to defence.
The Legal Framework: Clarity and Effectiveness
The requirements for administrative notifications in Spain are set out primarily in the Law 39/2015 on Common Administrative Procedure and in the General Tax Law (Ley General Tributaria).
- Article 40.2 of Law 39/2015 requires that a notification include either the full text of the resolution or a sufficiently detailed summary to understand its content and effects, together with the issuing authority and the date.
- Article 41.1 makes clear that the administration must ensure effective communication, not merely an attempted delivery.
- Article 44 recognises publication in the Boletín Oficial del Estado (BOE) as a measure of last resort — only permissible once all other means have failed.
Within tax proceedings, Articles 109 and 110 of the General Tax Law strengthen these guarantees by requiring complete disclosure of the act and verification of the taxpayer’s current address.
In short, a notification is only valid when it genuinely reaches the taxpayer and conveys the legal meaning of the act being served.
Persistent Defects in AEAT Practice
In cross-border tax matters, notification irregularities are more common than they should be. The AEAT often relies on outdated addresses, fails to exhaust reasonable delivery methods before resorting to edictal publication, or issues incomplete delivery certificates.
It is not unusual for non-resident taxpayers to be automatically enrolled in electronic notification systems without meeting the legal criteria for doing so. Each of these errors undermines the legality of the administrative act itself.
From a procedural standpoint, an act that has not been validly notified has no effect — and cannot serve as the legal basis for HMRC recovery in the United Kingdom.
International Cooperation and HMRC’s Duties
The cooperation framework between Spain and the UK originates in Directive 2010/24/EU on mutual assistance for the recovery of tax claims, which the UK continues to apply through retained and bilateral arrangements.
Under that system, HMRC may act as the recovery agent for Spanish tax debts. However, its authority to do so depends on the validity of the Spanish administrative act. If the underlying act has not been properly notified, it is not enforceable in Spain — and cannot be enforced in the UK.
When a taxpayer challenges a Spanish notification, HMRC is obliged to suspend enforcement until the Spanish proceedings have been resolved.
What Taxpayers Should Do
Anyone receiving an HMRC demand for a Spanish tax debt should immediately review the Spanish notification process. This includes verifying the address used, the delivery attempts made, and whether the act itself was clearly identified.
Under Spanish law, limitation and appeal periods only begin to run once a valid notification occurs. A defective notification can therefore reopen the possibility of appeal, even long after the original act was issued.
At Del Canto Chambers, we conduct detailed reviews of notification records, identify procedural defects, and initiate challenges before the AEAT and Spanish administrative courts. At the same time, we coordinate with HMRC to ensure enforcement is suspended while the Spanish proceedings are pending.
Conclusion
Proper notification is more than a procedural formality — it is a cornerstone of the rule of law. The Supreme Court’s 2025 judgment confirms that administrative acts must be communicated with clarity and precision if they are to have any legal effect.
For UK taxpayers facing cross-border collection, this principle provides powerful grounds for defence. A defective notification in Spain may not only invalidate the tax assessment there, but also halt enforcement by HMRC in the United Kingdom.
At Del Canto Chambers, we believe that procedural rights are substantive rights. Upholding them is not just about technical compliance — it is about ensuring fairness, transparency, and genuine access to justice across jurisdictions.
