The Supreme Court upholds the right against self-incrimination in the tax sphere

The Supreme Court, in two judgments dated 4 December 2025 and 10 December 2025, has established the parameters that must be used to apply the right against self-incrimination in the tax sphere. It is true that, previously, the Supreme Court had already made some reference to this issue; however, in these two judgments the Court sets out, in a much more concrete and detailed manner, how this right is to be applied in the relationship between taxpayers and the tax authorities.

The right against self-incrimination is recognised both in the European Convention on Human Rights and in the Spanish Constitution. Article 24 of the Spanish Constitution provides for the right “not to testify against oneself, not to confess guilt, and to the presumption of innocence”.

The application of this right is beyond dispute in the criminal sphere, but in the tax sphere the situation is more complex. Although it is well established that the same principles applicable in criminal law apply to administrative sanctioning proceedings, the specific features of the tax system must be taken into account. In the tax context, citizens are under a legal obligation to cooperate with the tax authorities by providing any documentation relevant for tax purposes. In other words, on the one hand, the law requires a taxpayer to provide information to the tax authorities (which may then use it to issue an assessment and/or impose penalties), while on the other, the taxpayer has the right to remain silent and not to incriminate themselves.

In these two judgments (the judgment of 10 December 2025 reiterates the reasoning of that of 4 December 2025), the Court addresses this conflict, analysing the limits of the obligation to provide documentation to the tax authorities when that documentation may in turn be used to impose tax penalties.

These two judgments are not favourable to the taxpayers who brought the appeals; nevertheless, they establish criteria which will undoubtedly promote the effective application of the right against self-incrimination and will require the tax authorities to provide a much more robust justification when imposing penalties.

Broadly speaking, the right against self-incrimination includes:

• The right not to testify against oneself
• The right not to confess guilt
• The right to remain silent

As noted above, in the tax sphere the taxpayer has an obligation to cooperate with the tax authorities. However, this obligation is not absolute: it does not mean that the taxpayer is required to confess. The taxpayer is obliged to provide existing documentation, but cannot be required to produce explanations from which the subsequent imposition of a penalty may arise.

In these judgments, the issue was whether, in the course of a tax inspection procedure, the taxpayer could refuse to provide invoices requested by the Tax Agency, and what consequences the fact of having been compelled to produce them—under threat of a penalty for obstruction or resistance to the inspection—would have in subsequent penalty proceedings. According to the appellant, the obligation to provide these invoices amounted in practice to a negation of their right against self-incrimination.

The Supreme Court rejects this argument and states that both invoices and accounting records must be provided in compliance with a legal obligation, and that this excludes the possibility of considering such provision as a breach of the taxpayer’s right against self-incrimination.

Furthermore, it was not the mere provision of invoices that triggered the imposition of penalties. What justified those penalties were the discrepancies between the documents provided and the taxpayer’s commercial, business and employment reality, as it was established that the taxpayer lacked the material and human resources necessary to carry out the activity for which the invoices had been issued.

The judgments also include a brief analysis of the content of the right against self-incrimination from the perspective of the European Court of Human Rights. Having clarified the issue, the Supreme Court concludes that the Tax Agency may only use, for the purpose of imposing tax penalties, documentation that:

• Is public (for example, contained in public registers)
• The taxpayer is legally required to hold (such as invoices and accounting records)
• Exists independently of the will of the person concerned (for example, obtained through requests to third parties)
• Has been voluntarily provided by the taxpayer as part of their defence strategy

What is not permitted is to compel the taxpayer to answer questions from which their guilt may be inferred.

As a result of the above, the Tax Agency will have to assess the documentation obtained during inspection proceedings in order to determine which material may be used to impose a penalty and which may not be used because doing so would infringe the taxpayer’s right against self-incrimination.

In other words, it is now clear that there will be documentation which the Tax Agency may use to issue a tax assessment, but which it may not use to impose a penalty. This situation illustrates a principle that is already well known (and applicable independently of the right against self-incrimination), namely that there is evidence which may be sufficient for assessment purposes but not for the imposition of penalties.

In summary, following these Supreme Court judgments, it will be even more important to pay close attention to the strategy adopted during tax inspections and subsequent tax litigation where there is a possibility of tax penalties being imposed.

Finally, one last reminder: the right against self-incrimination applies only in sanctioning proceedings, not in the issuing of tax assessments.