Fifty Years of the Tax Constitution (VII): Assessment and Conclusions on Half a Century of Constitutional Tax Case Law

Half a century after the approval of the Constitution of 2 April 1976, the trajectory of the Constitutional Court in tax matters constitutes one of the richest chapters of Portuguese constitutionalism. Analysis of the rulings that make up the corpus of this study reveals an evolution marked by permanent tension between the financial and redistributive demands of the Social State and the defence of legal certainty, liberty, and the property of taxpayers. The quantitative data themselves — 44.7% findings of unconstitutionality (including 22 declarations with general binding force) against 53.8% findings of non-unconstitutionality, 70.6% of cases originating from concrete review, and 58.8% of rulings accompanied by dissenting opinions — demonstrate that the constitutional tax jurisdiction has never been a passive rubber-stamping forum for political power, functioning instead as an arena of vigorous doctrinal debate fuelled by contentious challenges brought by taxpayers.

Born of the compromise between a programme-constitution and a process-constitution, the 1976 Tax Constitution saw its protective dimension progressively refined by case law. From an initial review model based on the subjective test of arbitrariness and ad hoc balancing of the protection of legitimate expectations — evident in Rulings nos. 11/1983, 66/1984, and 141/1985 — the Court moved to a system of objective rules of guarantee. The textual consecration of the prohibition of retroactive taxes in the 1997 Constitutional Revision and the reading given to it by the Court from Ruling no. 172/2000 onwards converted Article 103(3) of the CRP into a guarantee analogous in nature to fundamental rights, freedoms, and guarantees, removing the temporal limit of taxation from conjunctural assessments of budgetary expediency.

Looking across the five phases traversed between 1976 and 2026, the jurisprudential heritage of the Portuguese Tax Constitution can be summed up in seven fundamental points:

(i) the democratic guarantee of self-taxation and the parliamentary statutory reserve, through which the Court established, from its very first decade, that not only the creation of taxes and the definition of their incidence and rates, but also the regime governing exemptions and tax benefits and even amendments more favourable to taxpayers belong to the exclusive competence of the Assembly of the Republic (save under a statute authorising the Government);

(ii) the delineation of sufficient determinability and the limits of open typicity, reconciling, from the mid-1990s onwards, the statutory reserve with material equality by admitting the use of indeterminate concepts and residual clauses to keep pace with new economic realities and curb tax avoidance, provided that an objective criterion of calculability reviewable by the courts is ensured;

(iii) the categorical prohibition of substantive tax retroactivity, grounded in the distinction between authentic retroactivity and retrospectivity and in the contrast between instantaneous taxable events (as in autonomous taxation) and taxable events of successive formation — a protection that over the past decade was extended to striking down disguised retroactivity enacted under the label of false interpretative laws;

(iv) the affirmation of ability to pay, proportional equality, and the dignified existential minimum as substantive limits on the apportionment of public burdens, both curbing arbitrary or disproportionate sacrifices in conjunctures of budgetary emergency and guaranteeing the absolute tax immunity of the portion of income indispensable to dignified survival;

(v) the autonomisation of the tertium genus of financial contributions accompanied by dynamic review of their temporality, overcoming the classical dichotomy between tax and fee through group equivalence, while requiring, in more recent years, that the successive renewal of ostensibly “extraordinary” contributions maintain an effective relationship of group benefit or causality, on pain of degenerating into unconstitutional sectoral taxes;

(vi) the curb on regulatory de-legalisation and the reserve of primary legislative function, clarifying that the absence of parliamentary approval of a general regime for financial contributions permits their creation by Government decree-law, but prohibits blank-cheque delegation of the essential elements of contributions or special tax regimes to a simple ministerial order or administrative regulation; and

(vii) the fullness of effective judicial protection, due process, and the prohibition of irrebuttable tax presumptions. This is a path that began with the abolition of the unappealability of administrative tax assessments and absolute enforcement privileges in the 1990s, proceeded through the guarantee of judicial control in tax enforcement and the protection of banking secrecy in the 2000s, and culminated recently in the declaration of unconstitutionality with general binding force of irrebuttable presumptions of tax incidence, securing the primacy of taxation of real income.

As this fifty-year cycle closes, it is this body of rules and limits — forged in constant dialogue between Ratton Palace, the tax courts, and legal scholarship — that will continue to be put to the test by new forms of action deployed by the tax administration1, the recurrent pressure to legislate by administrative or parafiscal means, and the growing compression of state tax sovereignty within the European and international framework2.