Testamentary Capacity and Succession Agreements in Later Life: A Spanish Perspective

Abstract

Population ageing is reshaping the assumptions on which succession law has traditionally rested. This article examines how Spanish succession law responds to this demographic shift through two closely connected dimensions: testamentary capacity and the growing role of succession agreements. The analysis adopts a doctrinal and comparative perspective within the Spanish legal system, taking account of the coexistence of the Spanish Civil Code and several autonomous succession regimes. It argues that testamentary capacity remains governed by a deliberately low and functional threshold, centred on the testator’s actual ability to form and express a testamentary intention at the time of execution, and that notarial ex ante control is central to preserving both autonomy and legal certainty. At the same time, relational vulnerability in later life requires distinct safeguards aimed at preserving testamentary freedom. The article further shows that succession agreements, often viewed as restrictions on testamentary freedom, may also operate as instruments of anticipatory autonomy. The central challenge is to make autonomy effective across time without confusing vulnerability with incapacity, or protection with constraint.

1. Preliminary Remarks

According to the United Nations Department of Economic and Social Affairs, Population Division (2024), the global population aged 65 and over is projected to reach 2.2 billion by the late 2070s, surpassing the number of children under the age of 18; by the mid-2030s, the number of persons aged 80 or over is expected to reach 265 million. The sustained increase in longevity disrupts the classical life course and turns later life into a stage of intense legal activity. Against this background, succession law emerges as a particularly sensitive field for analysing how legal systems respond to vulnerability and extended autonomy.

Today, succession law must operate in a context marked by structural ageing and increasingly complex living arrangements. Death rarely occurs at a time when descendants require protection; forced heirs are usually over fifty years old, and the deceased has often lived a long life characterised by intricate relational ties. In other words, the function of inheritance is not limited to downward economic promotion but increasingly concerns the recognition of affection and the organisation of care relationships in later life. Completing this picture is the concern of older persons regarding the destination of their estate, whether motivated by a desire for orderly planning or accountability towards family members and caregivers (Grimaldi 2004, p. 19).1

As the world prepares for an unprecedented transfer of wealth (UBS AG 2025),2 succession law must recalibrate its core concepts. Testamentary capacity and freedom were grounded in anthropological assumptions that no longer hold. Longevity introduces factors largely alien to classical theory: the relational vulnerability of the testator, the presence of caregivers, affective ties outside the traditional family… These elements help explain why individuals may choose to limit their testamentary freedom through inter vivos commitments to secure long-term care or protect themselves against future vulnerabilities.

This paper focuses on two dimensions that are especially pertinent for older persons: testamentary capacity and the growing role of binding mortis causa dispositions (succession agreements). The analysis adopts the perspective of Spanish succession law. Spain constitutes a genuine laboratory in this field, with seven distinct succession regimes operating under the same constitutional framework. Alongside the rules of the Spanish Civil Code of 1889 (SCC), six autonomous systems have developed their own distinctive features. The SCC is formally in force throughout Spain, but its succession rules are directly applicable in only eleven of the seventeen Autonomous Communities, as well as in the North African cities of Ceuta and Melilla. In Aragon, Catalonia, Galicia, Navarre, the Basque Country and the Balearic Islands, by contrast, succession law is primarily governed by autonomous civil-law systems,3 adopted pursuant to the constitutional competence of those Autonomous Communities to “preserve, modify and develop” their own civil law.4 This normative plurality affects the basic architecture of succession law and generates complex conflicts of laws, while at the same time fostering dynamics of comparison and, in some cases, constructive emulation.

Against this background, the Spanish experience provides a useful lens through which to assess how testamentary capacity and succession agreements are being reshaped in response to vulnerability and extended autonomy in later life.

2. Testamentary Capacity

2.1. The Open Notarial Will as Point of Reference

The use of wills in Spain is notably widespread, reflecting a strong testamentary culture (Delgado Echevarría 2006, pp. 106–15; Consejo General del Notariado n.d.).5 This recurrently observed feature distinguishes Spain from other European jurisdictions where intestacy plays a more prominent role (Cámara Lapuente 2011, p. 72).

Among the various testamentary forms, the unilateral open will executed before a notary is by far the dominant type (Consejo General del Notariado n.d.).6 The reasons for this predominance are well known. The open notarial will is inexpensive (typically between €38 and €80)7 and legally robust. Its low cost facilitates access—indeed, it may be regarded as a quasi-public service; the intervention of the notary ensures authenticity (prevents forgery), legality, and safekeeping, and confers upon the instrument the enhanced probative force characteristic of public documents; these advantages contrast with the risks commonly associated with holographic wills (Cámara Lapuente 2011, p. 85; Manresa y Navarro 1910, vol. 5, p. 291; Vaquer Aloy 2022, p. 19).8 As a result, upon death, no additional judicial or administrative procedure is required for the open notarial will to take effect (Reid et al. 2011, pp. 433–34).

This structural predominance carries a clear methodological implication. The internal plurality of Spanish succession law is less disruptive in the field of testamentary forms, and especially in relation to the open notarial will. Spanish legal systems may differ as to certain formal requirements, but the basic structure of the open will executed before a notary is substantially common. The following analysis therefore takes the open notarial will as its point of reference and approaches testamentary capacity from a broadly Spanish perspective, drawing on specific divergences only where they are relevant to the argument.

2.2. Capacity, Freedom and Expression

From a subjective perspective, a will presupposes three conditions on the part of the testator. The first is the ability to form a dispositive intention in contemplation of death: testamentary capacity in the strict sense. The second is that this intention has been formed freely, without coercion or undue influence: testamentary freedom.9 The third is that the intention can be expressed and made known: the capacity for communication or expression.

The distinction is straightforward, but it is worth making explicit, as the three elements do not necessarily coincide. A person may understand and intend, yet be unable to communicate that intention adequately; may be able to communicate, yet have formed the decision under pressure or undue influence; or may appear to intend a particular outcome without possessing the minimum level of discernment required for that decision to be attributed to them. This part of the paper focuses on testamentary capacity and its exercise, while referring more selectively to testamentary freedom. Testamentary expression, including the use of communication aids in the notarial process, falls outside the scope of the present study.

2.3. The Requirements for Testamentary Capacity

Testamentary capacity in Spanish systems is structured around two requirements: on the one hand, a minimum age and, on the other, natural capacity. The former is an objective and predetermined requirement; the latter is functional and case-specific. There is, by contrast, no maximum age limit. This formulation reflects a long-standing tradition in which capacity is the rule and incapacity the exception (Comes 1826, vol. 1, p. 434, § 1027).10

2.3.1. Age

Unlike natural capacity, which requires an assessment of the testator’s actual condition at the time of execution, age operates as an abstract rule that is easily verifiable. It does not directly measure discernment but presumes it on the basis of a legally defined threshold of maturity. In this sense, it functions as a proxy for natural capacity: it simplifies the issue, albeit inevitably at the cost of a certain loss of sensitivity to the individual case.

In Spanish systems, the minimum age for executing a will before a notary is set at fourteen.11 The rule, of Romanist origin,12 relates to other classic strictly personal acts, such as the recognition of filiation and marriage, which likewise presupposed puberty in Roman law. These are acts belonging to the most intimate sphere: they must be performed personally, yet the legal system does not require a demanding standard of capacity, but only a minimum level of maturity. It should be recalled that a will is essentially revocable and produces no effects during the testator’s lifetime. The risks associated with premature decision-making are therefore structurally limited.

That said, a will is not a trivial act. On the contrary, it is imbued with a clear moral and social dimension, insofar as it expresses a decision regarding the post-mortem destination of one’s estate (Braun 2024). For this reason, the threshold of fourteen may appear low: it has no parallel in the European context13 and has largely lost its historical justification.14 However, the practical relevance of this objection is limited. Wills made by minors are exceedingly rare and, above all, the system mitigates the associated risks by allowing them only in notarial form.15 Accordingly, the capacity of a minor who has reached puberty to make a will may be regarded as a historical anomaly rather than a genuine source of dysfunction, particularly since one can conceive of situations in which it is appropriate for such a minor to be able to dispose of their estate (Muñoz 2021, p. 337; Law Commission 2025, para. 10.51).16

Far more significant for the purposes of this paper is the absence of a maximum age limit. In theory, the legislator could establish a symmetrical rule at the opposite end of the life cycle, invalidating wills executed beyond a certain age on the premise that, from that point onwards, the understanding required for testation becomes as unlikely as in childhood (Hirsch 2017, p. 307). However, such a solution would run up against reality—it is both natural and common to wish to arrange one’s succession at the end of life—and would also be difficult to reconcile with contemporary standards of fundamental rights, insofar as it would exclude individuals solely on the basis of age, irrespective of their actual mental capacity, raising concerns of age discrimination.17

It would moreover run counter to a principle already articulated in Roman law, according to which neither old age nor bodily illness deprives a person of the capacity to make a will, provided that mental lucidity is preserved.18 Nonetheless, classical thought had already recognised the specific risks associated with decisions taken at the last moment or in terminal conditions. Plato warned that a person near death may lack the firmness of mind required to remain faithful to their own settled intentions (Plato 2005, Book XI, pp. 922e–3a). These concerns were, in turn, reflected in certain French customary rules described by Domat, under which mortis causa dispositions were declared null if the testator did not survive for a specified period after making them (Domat 1829, pp. 822, 1028).

As might be expected, modern Spanish legal systems do not follow this path. They do not presume incapacity based on old age, illness, or proximity to death; rather, they locate the issue in natural capacity. Beyond the age of fourteen, the only limit is therefore the degree of discernment and understanding at the time of execution. A distinct matter is vulnerability, often associated with advanced age, which may justify specific safeguards. But this does not concern testamentary capacity in the strict sense; it concerns instead the freedom with which the decision is formed, an issue addressed below in Section 3.

2.3.2. Natural Capacity

Beyond the formal requirement of age, testamentary capacity in Spanish systems rests on what this article refers to as “natural capacity”, a term that is gaining consolidation in the Catalan Civil Code (Parlament de Catalunya 2024).19 Legal systems express it in different ways—e.g., cabal juicio, sain d’esprit, capacità d’intendere e di volere, sound mind—20 yet all point to the same underlying idea: the need for sufficient discernment and understanding. This conception was already present in Roman law21 and in the classical formulations that later shaped contemporary common law standards (Blackstone 1766, vol. 2, p. 496).

In recent decades, particularly following the United Nations Convention on the Rights of Persons with Disabilities of 2006 (UNCRPD), legal language has been refined, moving away from stigmatising categories22 without altering the core requirement. Its long-recognised indeterminacy, however, persists (Manresa y Navarro 1910, vol. 5, p. 293).23 Natural capacity is required without further specification, so that the issue is ultimately left to its application. It is therefore a practical question, to be determined case by case.

The threshold is a minimal one. Testamentary capacity does not require a state of full lucidity, but only sufficient discernment to understand the nature and basic consequences of the act. This reflects the nature of the will itself: an act that is, in principle, harmless to the testator, as it produces no effects during life and remains revocable until death. In this context, the function of the capacity requirement is not primarily to protect the testator—who assumes no immediate patrimonial risk—or even the family—who benefit from other protective mechanisms, notably forced heirship—but to ensure that the disposition is genuinely attributable to the testator.

From this perspective, the existence of medical conditions is not decisive; what matters is their actual impact on the testator’s understanding and volition. The assessment of capacity is therefore not a medical judgement, but a legal one directed at a factual question: whether the testator possessed, at the time of execution, the minimum level of discernment required to form a will of their own.

The main practical difficulty arises in intermediate cases. In many situations—particularly in contexts of ageing and progressive cognitive decline—capacity does not present itself as a clear-cut reality, but as a fluctuating condition. The issue is not one of clearly capable or clearly incapable individuals, but of borderline situations in which discernment is only partially preserved or gradually deteriorating. It is in this “twilight zone” that most disputes arise (Law Commission 2025, para. 2.5, citing Munro and Newhall 2023).24

In this context, testamentary capacity ceases to be a static requirement and becomes a standard shaped by destabilising circumstances, ranging from degenerative diseases to medication with cognitive side effects or the need for urgent decision-making. Illness—including neurodegenerative conditions—does not in itself entail incapacity but introduces uncertainty into its assessment. Everything depends on the degree of impairment and, above all, on the testator’s condition at the precise moment of execution. The inquiry must therefore be resolutely case-specific, focusing on whether, at that particular moment, the testator retained sufficient understanding (and volition) for the act performed. This, in turn, places particular weight on the mechanisms through which such an assessment is made.

2.4. Control of Testamentary Capacity

In Spain, testamentary capacity is subject to a dual system of legal control. On the one hand, there is an ex ante, preventive control exercised by the notary at the time of execution. On the other, an ex post, contingent control carried out by the courts in the event of a challenge. These mechanisms are complementary: the former aims to prevent disputes, the latter to resolve them once they arise.

2.4.1. Ex Ante Control: The Notarial Assessment of Capacity

Preventive control of capacity is inherent in the notarial form. The notary identifies the testator—thereby ensuring the authenticity of the will—and assesses their capacity. This marks a decisive difference from holographic and other private wills, in which both authorship and capacity can only be reviewed after death. In the notarial will, control is brought forward to the moment of execution: to borrow common law terminology, the will is born “probated”.25

This control is known as the “juicio notarial de capacidad” (notarial assessment of capacity), which must be incorporated into the instrument26 and reinforces the general presumption of capacity.27 Succession law and notarial legislation impose on the notary the duty to assess capacity but provide neither detailed criteria nor specific methods for doing so.28 The system thus rests largely on the notary’s prudence and practical sense.

The notarial assessment of capacity is based on the direct examination of the testator. Preliminary elements—initial contact with the notary’s office, impressions of staff, or information provided by third parties—may be relevant,29 but the decisive moment is the execution itself. It is not a clinical examination (the notary is neither trained nor expected to be trained in psychiatry or neurology), but a sufficiently probing inquiry to ascertain that the testator understands the nature of the act and can express a will of their own. In basic terms, the testator must be able to orient themselves in time and space, identify their personal and family circumstances, understand that they are disposing of their property upon death, and coherently express their intentions, recognising as their own the last will drafted and read aloud by the notary. Beyond this, the law requires neither sophistication nor eloquence from the testator, nor reasonable or fair dispositions (Jou i Mirabent 2009, pp. 179–80).

In the current context—marked by increasing longevity and advances in the diagnosis and treatment of neurodegenerative conditions—the assessment of capacity has become a delicate task. The notary must ensure access to testation without authorising dispositions that fall below the minimum threshold of discernment, and must do so under the additional pressure of increasing litigation, especially where wills are executed shortly before death or in hospital or care settings (Col·legi Notarial de Catalunya 2016).30 The temptation to adopt an overly cautious stance in order to avoid liability is understandable, but legally misplaced: the notary must not refrain from acting in cases of doubt, but should instead deepen the inquiry until a sufficiently grounded judgement can be formed.

In response to these challenges, notarial practice has developed a range of safeguards aimed at reinforcing the reliability of such assessments. There is no—and likely should not be—a closed legal protocol: an overly standardised system would risk turning the absence of any given safeguard into an automatic ground for challenging the notarial judgement. What exists instead is a flexible lex artis, adaptable to the circumstances of each testator, in which different safeguards may be used either as alternatives or in combination.

The opinion of two medical practitioners constitutes the classical safeguard (Gibert 1875, p. 212; Law Commission 2025, para. 2.134).31 Catalan law still expressly permits the notary to request it, requiring that, if obtained, it be recorded in the instrument and that the practitioners sign the will together with the notary.32 Today, however, it no longer operates as an additional will formality, but as an auxiliary tool.33 It does not replace the notarial assessment, nor relieve the notary of responsibility: if not convinced of the testator’s capacity, the notary must refuse to execute the will, regardless of a favourable opinion. In practice, its value lies less in persuading the notary than in externally reinforcing an already formed assessment and anticipating its defence in litigation. It thus functions as a form of pre-constituted evidence. In an ageing society, where the use of such opinions is likely to increase, greater institutional coordination between legal and medical professionals should be promoted—for instance, through professional bodies—to ensure their availability under conditions of quality, timeliness and reasonable cost.

Instead of seeking external medical opinions, some notaries use brief cognitive tests to introduce a degree of objectivity into the evaluation of the testator’s mental functioning (Pfeiffer 1975; Gomá 2006). They may serve as complementary evidence, particularly where their results are properly documented; however, their use must remain cautious: the notary is not a healthcare professional and it is not always appropriate to subject the testator to them, especially where this would be intrusive or unnecessary. At present, this practice remains largely ad hoc: some notaries use such tools, others do not, and those who do may rely on different tests. This, in turn, points to the need for greater engagement between the legal and medical professions, so that medical practitioners have a precise understanding of the legal nature of testation and its relatively low threshold of capacity, and can accordingly develop or recommend cognitive tests specifically tailored to testamentary decision-making.

Alongside these more medically oriented safeguards, notarial practice may also resort to measures of a strictly legal or evidentiary nature. One such measure is the possibility for the notary to document the process by which a positive assessment is reached (for example, by noting that the testator was asked relevant questions and responded coherently, was able to identify close family members and provide a reasoned explanation of the intended distribution among them…). Although not mandatory, this constitutes good practice (Garrido Melero 2020, pp. 94–95; Gibert 1875, p. 34),34 both for its evidentiary value and for its deterrent effect against subsequent legal challenges.

The notary may also request the presence of witnesses at the execution of the will. Their role is not to assess capacity—which remains the exclusive responsibility of the notary—but to reinforce the evidentiary framework of the execution.35 It may be useful in borderline cases, although it carries a certain ambivalence: it should not be interpreted as an indication of doubt, but rather as a measure of prudence, while also requiring due regard for the testator’s privacy.

Audiovisual recording may also be considered, subject to the testator’s consent. This measure makes it possible to preserve a direct record of the execution, including non-verbal elements that are difficult to reconstruct ex post. Its evidentiary value can be significant and may also have a deterrent effect against subsequent legal challenges. The recording may be kept under the notary’s custody, with a simple reference in the instrument to its existence.36 That said, its use calls for particular caution, given the privacy concerns involved and the risk that the formality of the setting may affect the testator’s spontaneity.

All these safeguards respond to a sound underlying rationale, particularly in the context described. Their use, however, calls for restraint. As a matter of principle, capacity must be presumed irrespective of age or any other circumstance. In practice, however, this starting point may shift: where certain profiles are frequently associated with difficulties of discernment, recourse to medical opinions or other safeguards tends to become routine. The risk is that, in seeking greater legal certainty, such practices may ultimately undermine the very principle they are intended to protect, resulting in differentiated—and potentially discriminatory—treatment of certain individuals.

2.4.2. Ex Post Judicial Control

Ex post control is exercised by the courts in actions for nullity based on the testator’s lack of capacity. It is structurally problematic: the testator—key witness—is no longer available for examination, and death may have occurred long after the will was executed.

Since capacity is presumed, the burden of proof lies on the claimant. In the case of notarial wills, that burden is heavier, since the general presumption of capacity is further reinforced by the notary’s ex ante assessment. That assessment, however, is not a scientific finding, but a professional judgement based on a prudent and necessarily probabilistic appraisal. Even when supported by the safeguards described above, it is not the outcome of adversarial proceedings—since those whose succession rights may be affected have not taken part in the process—and therefore it does not have the status of evidence tested in court. Accordingly, notarial wills are not immune from contestation. Yet the reinforced presumption of capacity can only be displaced by evidence of exceptional weight and cogency.37 This immediately raises a further question: what kind of evidence may satisfy that demanding threshold?

Since the notarial will already embodies a positive assessment of capacity, such evidence must necessarily be extrinsic—that is, evidence obtained outside the instrument itself. It will typically consist of medical records, expert opinions, or witness testimony. Courts tend to accord limited probative value to retrospective reports prepared by practitioners who did not treat the testator at the time of execution, while attaching greater weight to observations made by professionals with direct knowledge of the testator’s condition (Vaquer Aloy 2024, p. 51).38 Lay witness testimony, by contrast, will rarely be decisive on its own; its value is mainly corroborative, especially where it converges with contemporaneous medical evidence or with the testimony of professionals who directly observed the testator.39 Parties sometimes—questionably—seek to call the authorising notary. Yet the notary has already assessed capacity and attested to the content of the instrument; further testimony is therefore generally inappropriate (Pujol Capilla 2017). A different situation arises where another notary, other than the one who authorised the contested will, had previously refused to execute a will for the same testator. In such cases, that testimony may carry significant evidentiary weight.40

The fact that the evidence capable of rebutting the notarial judgement is, by definition, extrinsic does not mean that the instrument itself is irrelevant. Courts assess capacity in relation to the particular will, taking into account the content and complexity of its provisions. A simple appointment of an heir or a straightforward legacy may require only a basic understanding of the nature and effects of the act.41 By contrast, wills involving complex substitutions, conditional clauses or significant departures from previous testamentary schemes may call for a more demanding appraisal of the testator’s actual understanding.42 The point is not that the law creates separate standards of capacity, but that a formally minimal threshold must be judicially tested against the cognitive demands of the particular disposition.43 Complexity, however, should not be confused with the mere use of technical legal language. One of the notary’s functions is precisely to translate into legal form intentions that may have been expressed in ordinary terms. A will may therefore be legally sophisticated without necessarily requiring an unusually high degree of cognitive ability, provided that the underlying intention was simple and clearly understood by the testator. Conversely, even a formally simple will may raise concerns if its practical consequences were not grasped. In this respect, the fact that Spanish law allows testation from the age of fourteen confirms that the required level of discernment is generally modest, at least where the dispositions are straightforward.44

Taken together, these considerations show that judicial control is indispensable, but must remain exceptional, so as to keep litigation within narrow limits. The system relies primarily on preventive control, thereby placing a central responsibility on the notary: to ensure that the will reflects the testator’s own intentions while respecting their wishes and preferences within a framework of broad and relatively low-cost access to testation. Where this preventive function has been exercised diligently—including, where appropriate, the use of safeguards—subsequent attempts to set the will aside should ordinarily fail. Yet neither error nor abuse can ever be entirely excluded. This is why judicial review must remain available. What the law ultimately offers is a reasonable balance between autonomy and protection, while accepting that some margin of uncertainty is unavoidable.

2.5. Exercise of Testamentary Capacity: The Strictly Personal Nature of the Will and Supported Will-Making

A will is a strictly personal act (personalísimo, art. 670 SCC). This characterisation excludes any form of representation or delegated decision-making: no one may decide for the testator, nor make, amend or revoke a testamentary disposition on their behalf. Consequently, where a person lacks testamentary capacity and no substitute mechanism is legally available, the destination of their estate will be determined either by the rules of intestacy, if no valid will was previously made, or by an earlier valid will that the person is no longer able to amend or revoke.

Traditionally, this rigidity was partially mitigated by the Roman-law devices of pupillary and exemplary substitution. Often regarded as exceptions to the strictly personal nature of the will (Marsal i Guillament 2000, pp. 170–202), these mechanisms made it possible to appoint an heir for persons who could not make a will themselves—minors below the required age and persons with impaired mental capacity—and thus to avoid the automatic application of intestacy, an outcome regarded in Roman law as especially undesirable. Exemplary substitution, in particular, allowed an ascendant to appoint an heir for a descendant with a disability who was unable to testate.

Yet Law 8/2021, adopted to align Spanish law with the UNCRPD, abolished exemplary substitution in the SCC without introducing any functional replacement, on the basis of a brief and unconvincing justification (Pérez Ramos 2021, p. 174).45 This choice has been criticised by some authors (e.g., de Amunátegui Rodríguez 2021, p. 929; Domínguez Luelmo 2024, p. 33), who argue that the institution could still perform a useful role: it made it possible to favour those who had cared for the person with a disability, thereby encouraging such care, while avoiding the rigid outcomes of intestacy. Catalan, Balearic and Aragonese civil laws, by contrast, have chosen to retain exemplary substitution.46 This contrast raises a broader question: whether the strictly personal nature of the will should ever be qualified in order to avoid succession outcomes that may be contrary to the hypothetical wishes of an adult unable to testate, whether they arise from intestacy or from an earlier will that the person can no longer amend or revoke. Should such an exception be accepted, it is not self-evident why it should remain confined, as in the current Catalan, Balearic and Aragonese models, to the classical substitution by ascendants for descendants, rather than being framed more generally and subject to appropriate safeguards (García Rubio 2018, p. 180).

The preceding debate concerns exceptional mechanisms of substitution. The post-UNCRPD framework, by contrast, shifts the focus from substitution to supported decision-making, raising a different question: whether support in the exercise of legal capacity can be reconciled with the strictly personal nature of the will. The key distinction is between the testamentary decision itself and the process through which that decision is formed, understood and expressed.

Given the strictly personal nature of the will, support measures that entail representation or the need for another person’s approval or consent are excluded. But does this also exclude assistance in understanding, deliberating and communicating one’s wishes, provided that the final decision remains the testator’s own? The decisive point is that support must remain facilitative. It may assist in the formation and expression of a testamentary intention, but it cannot supply that intention or operate as a legal complement to it. If, even with support, the person is unable to form and express a decision that can be attributed to them as their own, the issue is no longer one of supported will-making, but of lack of testamentary capacity.

This approach, however, currently has limited scope in Spanish succession law. Leaving aside support or reasonable adjustments required by sensory or physical disabilities47, there is no general model of “supported will-making” comparable to the broader supported decision-making schemes discussed after the UNCRPD (Law Commission 2025, chap. 4, paras. 4.1–4.3 and 4.95–4.98). The testator may, of course, have support measures in place for the exercise of legal capacity, and may also seek advice from or deliberate with third parties before executing the will. Indeed, in many cases such prior or informal assistance may be essential for the testator to clarify their wishes and understand the consequences of different options. But these forms of preparatory assistance have no autonomous legal role in the execution of the will and do not alter the strictly personal character of the testamentary decision.

In testamentary matters, Spanish law therefore channels Convention-based support measures for the exercise of legal capacity primarily through the authorising notary. The SCC and the CDFA reflect this role by expressly requiring the notary to help the testator develop their own decision-making process, supporting understanding and reasoning and facilitating, with the necessary adjustments, the expression of their will, wishes and preferences (Consejo General del Notariado 2021).48 The notary is therefore not merely the drafter of the instrument, nor simply an external assessor. Rather, the notary performs a dual institutional role: as support provider, by facilitating the testator’s own understanding and articulation of testamentary intention (Guilarte Martín-Calero 2014, p. 629); and as a safeguard, within the meaning of art. 12(4) UNCRPD, by ensuring that the testamentary act remains conscious and free. This safeguard function requires the notary to verify that any prior or surrounding assistance—whether provided by formally appointed supports, relatives, caregivers or other trusted persons—has not become pressure or undue influence. It does not incorporate third-party supports into the testamentary act but serves to confirm that the final disposition is attributable to the testator as their own free decision. Yet this same function also reveals the limits of a purely capacity-based analysis. Even a testator who understands and can express a testamentary intention may have formed it under pressure or undue influence. The analysis must therefore turn from the ability to make a will to the freedom with which the testamentary intention is formed.

2.6. Testamentary Freedom

Testamentary freedom is closely connected with testamentary capacity, but it operates on a different plane. Whereas capacity concerns the ability to understand and intend, freedom concerns the conditions under which testamentary intention is formed. In this sense, intact cognitive capacity does not preclude the testator’s decision from being shaped—or even distorted—by loneliness, dependency or care needs. The figure of the captator or heredipeta—i.e., the person who cultivates a relationship with the testator in the hope of obtaining a testamentary benefit—is a classical one (Champlin 1991, pp. 87–102, app. IV),49 but it acquires renewed significance today in a society with a growing number of older persons living alone, in care homes, or dependent on third parties (Instituto Nacional de Estadística 2024; Instituto de Mayores y Servicios Sociales 2025).50

As a specific means of protecting testamentary freedom, Romanist legal systems rely on the classical doctrine of defects of consent—fraud, intimidation and violence—which may lead to the nullity of the will.51 In the testamentary context, however, this framework has limited practical effectiveness. The difficulty is not merely evidentiary, although proof is undoubtedly problematic: an action for nullity can be brought only after the testator’s death, when direct evidence of the circumstances in which the will was formed is often unavailable.52 It is also conceptual. Fraud, intimidation and violence presuppose relatively identifiable acts or episodes, whereas contemporary forms of captation often operate through cumulative and diffuse processes of influence. There may be no fraud, coercion or violence in the strict sense, but rather gradual shaping of the testator’s preferences, through dependency, isolation or emotional pressure. These are grey areas in which the testator’s intention may be conditioned without meeting the technical requirements of a defect of consent. As a result, defects of consent play only a limited role in testamentary litigation. Where captation and vulnerability are at issue, challenges are often framed, where the facts permit, also on the ground of lack of natural capacity.53 This does not collapse freedom into capacity but reveals the practical limits of the traditional doctrine of vitiated consent.

Against this background, mechanisms that operate beyond—or in addition to—the classical doctrine of defects of consent acquire particular relevance. Their function is not only to react ex post to a vitiated testamentary intention, but also to control situations of heightened risk before they produce succession effects.

Spanish succession systems have long provided for rules of relative incapacity or disqualification to inherit (inhabilidad), which render ineffective testamentary dispositions made in favour of certain persons who, because of their relationship with the testator or their role in the execution of the will, may have played a decisive part in shaping its final content.54 These rules operate as absolute prohibitions: the risk that the disposition may be the result of captation is considered so high that contrary evidence is not admitted. They also have a deterrent effect, since they deprive any attempt at influence of practical utility.

Originally, these prohibitions applied to notaries and other persons involved in the execution of the will (Díaz Alabart 1987, p. 112),55 religious confessors, and guardians of minors or incapacitated persons. In response to the growing number of vulnerable testators, the SCC has, since 2021, extended the prohibition to owners, managers and employees of facilities in which the testator is admitted for health or care reasons.56 Despite its effectiveness as a preventive measure, the rule has been criticised for not allowing proof that the disposition was genuinely free and therefore not the result of captation (Represa Polo 2021, p. 908; de Amunátegui Rodríguez 2019, p. 70).57 Yet this sacrifice appears, in my view, justified in institutional care settings, where the relationship between the testator and the care provider is marked by dependency and vulnerability, as well as theacute evidentiary difficulties involved. Allowing such proof would substantially weaken the preventive function of the prohibition and shift the dispute to a factual inquiry that can rarely be reconstructed after the testator’s death. The rule should therefore be understood not as a presumption of actual wrongdoing, but as a legal response to a structurally heightened risk, aimed at preserving testamentary freedom and the integrity of the care relationship.

A less intrusive alternative is to limit the available testamentary forms for such dispositions. This is the technique adopted by the SCC since the 2021 reform with regard to individual caregivers acting outside institutional care settings.58 The testamentary benefit is not prohibited, but it is made subject to notarial control: a disposition in favour of the caregiver may be made only in an open will executed before a notary. Notarial control thus serves as a preventive filter: if the notary is satisfied that the disposition is spontaneous, the will may be authorised; if captation is detected, authorisation must be refused (Vaquer Aloy 2015, p. 350). Form therefore operates as a guarantee—not as a restriction—of testamentary freedom.

This solution draws inspiration from Catalan law, which as early as 2009 subjected testamentary dispositions made in the context of care-related relationships to notarial control, whether the beneficiary was a natural or legal person and without distinguishing between institutional care and home-based assistance.59 The SCC, however, departs from that model and adopts, as the preceding analysis shows, a dual response: prohibition in institutional care settings and mandatory notarial control in other cases. This distinction is, in my view, sound. It reflects a logic of proportionality: the law neutralises testamentary benefits in institutional care relationships, while preserving gratitude-based dispositions in more personal care relationships, subject to notarial scrutiny.

In any event, beyond the differences between the SCC and the Catalan model, both approaches treat testamentary dispositions in favour of professional caregivers as inherently suspect and respond accordingly—either through prohibition or through mandatory notarial control. Yet these situations do not exhaust the possible cases of captation. Similar risks may arise, for instance, where a child who has frequent access to the testator progressively steers the testamentary decision in their favour, or where a new partner isolates the testator from their previous relational environment. It is therefore for legal professionals, and especially notaries, to remain attentive to other warning signs—such as the fact that, as often occurs, the person who contacts the notary’s office is not the testator, but a third party who stands to benefit substantially from the will.

This requires, in appropriate cases, a personal interview with the testator—preferably alone—and an inquiry into how the testamentary decision was formed, especially who initiated the process, whether it departs from previous wills, and whether the testator can explain the intended benefits. Particular attention should be paid to dispositions in favour of persons who have recently acquired influence over the testator, or whose role in the testator’s daily life may create dependence. The point is not to require the testator to justify their will in moral or familial terms, but to ensure that the disposition has a plausible personal explanation and is recognisably their own. Some of the precautions described above in relation to the notarial assessment of capacity may also be relevant here. Medical opinions or cognitive tests are directed primarily at natural capacity and will normally have little to say about freedom from undue influence. By contrast, procedural or evidentiary safeguards—such as witnesses, a brief record in the instrument of the questions asked and the reasons given by the testator, or, in appropriate cases, audiovisual recording—may help to show that the testamentary decision was formed spontaneously and free from improper pressure. A recent Catalan reform proposal illustrates the potential value and privacy risks of such safeguards (Generalitat de Catalunya, Departament de Justícia, Drets i Memòria 2023; Parlament de Catalunya 2024).60

Finally, from this perspective, forced heirship, despite its very different configurations across Spanish succession systems (Cámara Lapuente 2020),61 deserves at least a brief mention. Traditionally conceived as a restriction on testamentary freedom, forced heirship may also produce, in certain pathological cases, an indirect protective effect (Pérès and Potentier 2019, pp. 73–74). Where a testamentary disposition has been shaped by captation, the reserved share prevents the whole estate from being redirected as a result of that distortion (Lamarca i Marquès 2014, pp. 271–73). This does not change its dogmatic nature, but it shows that, in contexts of vulnerability and dependence, forced heirship may operate as a residual barrier against the most extreme effects of a distorted testamentary intention.

Taken together, these mechanisms show that testamentary freedom is far from an absolute space of private autonomy. In an ageing society, it is increasingly shaped by the tension between self-government and vulnerability. The challenge is therefore to design safeguards capable of preserving the authenticity of the testator’s intention without distorting the exercise of testamentary freedom itself.

3. Succession Agreements as Instruments of Anticipatory Autonomy

The preceding analysis of testamentary capacity and freedom points to a broader tension within the classical testamentary model. Revocability remains one of its clearest expressions. It allows the testator to retain the last word until death and to adapt their succession plan to changing circumstances. Yet, in later life, where ageing is accompanied by dependency or progressive exposure to relational pressure, the power to revoke may no longer operate solely as a guarantee of freedom; it may also become a source of vulnerability.

It is at this point that the appeal of binding succession instruments becomes apparent. Succession agreements allow a decision concerning the mortis causa destination of one’s estate to be stabilised through an inter vivos commitment. Thus, they should not be understood merely as restrictions on testamentary freedom. This section examines how, in appropriate cases, they may operate as instruments through which autonomy is exercised across time, enabling a person to bind themselves in order to secure a long-term care arrangement or to protect that decision from foreseeable vulnerability.

3.1. Succession Agreements in the Spanish Legal Landscape

The Spanish legal system offers a particularly useful setting in which to examine this form of anticipatory autonomy. While the open notarial will displays a relatively homogeneous structure across Spanish succession laws, succession agreements exhibit a much greater diversity. The SCC still maintains, in general terms, the classical prohibition of “contracts concerning future inheritance”.62 Such a restriction on private autonomy has long been questioned in scholarship (García Rubio and Herrero Oviedo 2016, pp. 1325–28; Olmedo Castañeda 2019, pp. 447–84) and is now being reconsidered, at least in part, within the SCC reform work launched by the Order of 4 February 2019 to review forced-heirship rules and freedom of testation (Ministerio de Justicia 2019); in this context, the admission of certain renunciatory succession agreements concerning forced-heirship rights is being explored (García Rubio 2026, pp. 113–42). By contrast, the autonomous communities with their own civil law admit succession agreements to varying degrees. The result is a heterogeneous framework, ranging from prohibition or exceptional admissibility to broad and structural recognition of contractual succession.63

This diversity has historical roots. In several Spanish territories, contractual succession developed in rural and family-based economies, where it served to preserve the integrity of the family estate and to organise intergenerational continuity. Modern legislation has transformed these traditional institutions, so that succession agreements are no longer confined to agrarian estates or marriage-based arrangements and have increasingly become instruments for the anticipatory organisation of patrimonial and personal relationships. Although they remain far less frequent than wills, notarial data reveal a striking increase in their use, with the number of succession agreements executed more than quadrupling from 7760 in 2011 to 31,150 in 2025 (Consejo General del Notariado n.d.).64

Yet, despite their modernisation and increasing use, succession agreements remain subject to a particularly cautious legal approach. Precisely because they restrict revocation, Spanish legal systems surround them with more stringent safeguards than those applicable to wills. Thus, whereas, as examined above, a notarial will may be made from the age of fourteen and requires only natural capacity, succession agreements are subject to a higher standard, usually described as “full contractual capacity”; and whereas testamentary law still admits, in many systems, private forms such as the holographic will, succession agreements must be executed in a public deed and therefore necessarily before a notary.65

The following analysis is not, of course, intended to reconstruct the detailed regulation of succession agreements in each Spanish system. Differences between territorial models matter—for instance as regards the subjective scope of the agreement, the admissible types of attribution, or the regime governing modification and termination—but they can remain in the background. What matters for the purposes of this article, and particularly from the perspective of later life, is their capacity to give binding force to anticipatory autonomy.

3.2. The Justificatory Basis of the Binding Effect

The key feature of succession agreements—what makes them both useful and problematic—is their binding nature. The concerns are well known: there is an increased risk of crystallising dispositions that may themselves have been shaped by captation;66 in the case of universal attributions, the future destiny of an estate whose composition is still uncertain becomes rigidly fixed; and, most fundamentally, the future de cuius loses the power of the “last word”—although relinquishing it may serve a useful function in some cases (Chami 1996, pp. 171–76)—.67

These concerns raise a central question. Why should a person who remains free to make and revoke a will choose instead to bind themselves? And why should a system that places revocability at the centre of voluntary succession permit such a restriction of the testator’s ability to change their mind? The answer lies in the function—or, to use the traditional civilian term, the cause—of the binding effect.68 A will, strictly speaking, has no such cause beyond the mere contemplatio mortis. In succession agreements, by contrast, it is precisely the binding effect that calls for an inquiry into the functions that justify their adoption. The attribution remains mortis causa, but the basis of the agreement does not lie in the attribution itself; it lies in the binding effect surrounding it. In this sense, the agreement is not chosen despite its relative irrevocability, but precisely because of it. The future de cuius seeks not only to determine the destination of certain assets or of the estate, but to stabilise a broader set of expectations. The binding effect is the legal technique through which that scheme is protected against later unilateral change.

In traditional universal succession agreements, the cause or function of the binding effect was inherent to the device itself: the intergenerational transmission of the family estate. Today, the same logic is reflected—albeit with necessary adaptations—in other legally relevant purposes expressly mentioned by legislation, such as the continuity of the family business and the provision of care or assistance to the future de cuius or to a member of their family.69 In these cases, the binding effect is not an abstract restriction of freedom, but the legal technique through which the specific purpose pursued is stabilised.

The agreement is thus linked to the pursuit of a specific objective or to the expected conduct of the beneficiary, so that frustration of that objective, or non-performance of that conduct, may give rise to termination of the agreement and the recovery of testamentary freedom. Against this background, legal scholarship has questioned whether the explicit statement of a justificatory basis for the binding effect should be required, casting well-founded doubt on whether mere contemplatio mortis is sufficient to explain a prior renunciation of testamentary freedom (Pintó Ruiz 2014–2016, pp. 537–56). In my view, the absence of an express statutory requirement should not, for that reason, lead to the binding effect being regarded as abstract or lacking substantive justification.

Within a framework of non-exhaustive statutory typicity, the concrete basis for the binding effect is left to private autonomy, subject to qualified notarial control. This is especially important in later life. I would argue that, where the agreement is concluded by a vulnerable person, the notary’s role cannot be limited to verifying formal capacity and abstract validity. It should also involve an inquiry into why a binding instrument has been chosen–that is, what interest it is intended to stabilise–and whether the restriction of future testamentary freedom is coherent with the person’s situation and expressed wishes. The point is not to assess the moral or economic desirability of the arrangement, but to ensure that the binding effect is intelligible as the legal expression of the person’s own succession plan. The more the agreement is presented as a response to future vulnerability, the more clearly the notary’s role in safeguarding the freedom with which it is concluded should come into play.

3.3. The Binding Effect in Later Life: From Care to Self-Protection

In later life, succession agreements may be used to secure future care by linking it to a stable mortis causa attribution. A will may express gratitude for care received, but it cannot by itself ensure the continuity of care still to be provided (Blasco Gascó 2019).70 By contrast, a succession agreement allows the prospective de cuius to organise, while still capable and autonomous, the legal framework for a future care relationship.

This function may be structured through different legal techniques. In broad terms, the provision of care may be configured as an obligation assumed by one of the parties in connection with the agreement’s defining purpose, as a charge imposed on the beneficiary,71 or through a clause making the continuation of the agreement conditional upon proper performance of the expected conduct.72 In all these configurations, non-performance by the beneficiary may give rise, at least, to termination of the agreement.73 The applicable legislation, however, does not always specify additional remedies or clearly define what amounts to non-performance, which makes it advisable for the parties to regulate these matters in advance and with sufficient precision.

General references to “care” or “assistance” may be insufficient, especially where the agreement is intended to operate over a long period and in circumstances of progressive dependency. The parties would therefore do well to specify, as far as possible, the content and intensity of the care to be provided: whether it entails cohabitation with the person cared for, regular visits, assistance with meals, medical appointments or daily activities, the time schedule or degree of availability expected from the caregiver, and the manner in which performance or non-performance is to be evidenced. They should also anticipate possible changes in the cared-for person’s condition, including the need for hospital or residential care, and clarify what duties would then remain incumbent on the caregiver. Particular attention should also be paid to the possibility that the caregiver predeceases the future de cuius. The automatic transmission of the caregiver’s contractual position to their heirs or descendants, as provided by default in some systems,74 may not correspond to the intentions of the future de cuius; they may instead wish to appoint a new caregiver or reserve the possibility of reorganising the arrangement.

At the same time, care-based succession agreements call for particular caution. They may secure care and help organise future dependency, but the very relationship that justifies the agreement may also place the caregiver in a position of influence over the future de cuius. This reinforces the importance of notarial control at the time the agreement is concluded. Where future dependency is foreseeable, the agreement may also involve trusted third parties in a supervisory role, for example to verify performance, mediate conflicts or alert to situations of abuse or neglect. Such mechanisms should not, however, be confused with a power to terminate or revoke the agreement. Since the mortis causa disposition is strictly personal, especially as regards the future de cuius, the decision to bring the binding arrangement to an end cannot, in principle, be delegated to a third party.75 This limit may be problematic where the protected person later becomes unable to react to non-performance or abuse. A possible solution could be to involve the trusted person not merely as supervisor, but as party to the agreement, and expressly confer on them the power to trigger termination in predefined circumstances.

Beyond securing care, succession agreements may also serve to stabilise a decision made while the person is still capable and free from pressure, before later vulnerability makes that decision more susceptible to external influence. Unlike the organisation of care, this function is not expressly typified in legislation but is confirmed by notarial practice (Gómez Taboada 2024, pp. 517–18).76

As the preceding section has shown, the classical testamentary model offers only an imperfect response to this concern. Ex post remedies based on lack of capacity or defects of consent are often evidentially fragile, while revocability itself may become a point of exposure where vulnerability increases over time. A free and well-considered will may later be revoked or altered under relational pressure. A succession agreement changes this dynamic. By making the succession decision binding, it may shield it from later pressure and prevent subsequent changes that no longer reflect the person’s settled preferences. In this sense, the future de cuius limits future testamentary freedom in order to preserve, rather than diminish, autonomy over time.

This protective function, however, necessarily presupposes that the initial decision was made freely in the first place. If the agreement itself is the product of pressure or captation, its binding effect merely stabilises the very distortion it purports to prevent. Beyond this, attention must also be paid to the subjective structure of the agreement. For this mechanism to operate effectively, the agreement should be concluded either with a trusted non-beneficiary party who, in principle, can be expected to consent to its termination or modification if the future de cuius so wishes, or, at least, not solely with the person from whom the influence may come, although this will not always be easy to ascertain. If, by contrast, that person is the only other contracting party, the same pressure may simply be redirected towards obtaining the consent of the future de cuius to undo or alter the arrangement. Here again, notarial control is decisive.

4. Concluding Remarks: Which Law of Succession for a Super-Aged Society?

The discussion of succession agreements brings the preceding analysis full circle. Whether succession decisions remain revocable or are stabilised through binding instruments, the central concern is the same: how succession law can preserve the authenticity of mortis causa decisions while taking account of the challenges of later life.

Three core principles underlie the Spanish legal framework examined above: capacity must be presumed, vulnerability must not be confused with incapacity, and safeguards should secure freedom rather than constrain it. Priority should therefore be given to ex ante mechanisms, chief among them the notarial function. Preventive rules against captation may be justified where strictly necessary, in order to neutralise structurally risky situations without disproportionately impairing testamentary freedom. Judicial control, though indispensable, should remain confined to pathological cases in which ordinary safeguards prove insufficient.

More broadly, succession law requires a careful balance between freedom and legal certainty. Ultimately, the task is to make autonomy effective across time, especially when dependence or cognitive decline places it under pressure.