Matizaciones del Tribunal Supremo a la conformación del expediente administrativo en las declaraciones de responsabilidad tributaria: análisis crítico de las sentencias de 18 de marzo de 2026, rec. nº 945/2024 y de 17 de abril de 2026, rec. nº 386/2024

Abstract

The Spanish Supreme Court rulings of March 18 and April 17, 2026 hold that article 24.2 of the Spanish Constitution requires that the taxpayer be able to assert, in any administrative or judicial appeals, not only the existence of defects —whether formal or substantive— in that declaration of liability or in the proceedings conducted for that purpose, but also all defects that may have occurred in the tax assessment or penalty proceedings from which such tax liability arises; even if they have become final for the principal debtor —who, however, will not be affected by whatever decision may be rendered—. This doctrine of the Supreme Court is complemented by the requirement, established in the judgment of March 18, 2026, that the liable part have access to the complete administrative files, the compilation of which is an administrative obligation, even if any defects therein were not raised by the appellant in the administrative proceedings, but only in the judicial proceedings. Otherwise, in so far as it leaves the liable party defenseless, a substantive —rather than formal— defect is deemed to exist, which precludes the retroactive application of proceedings so that the defect committed may be remedied administratively.