He who asserts must prove? Why that rule of thumb is too crude
Two former spouses are in dispute over gold they kept in a safe-deposit box. It is established that each is entitled to half of its value and that the husband removed the gold from the box in February 2022, which he communicated to the wife with a photograph. The wife claims delivery. The husband contends that he left the gold behind in the marital home and could no longer reach it after the wife changed the locks. The court of appeal places the burden of proving that contention on the husband, holds that he has insufficiently substantiated it, and therefore assumes that the husband still has the gold. The Supreme Court quashes (ECLI:NL:HR:2026:1292). The familiar rule of thumb "he who asserts must prove" suggests a simple answer, but it is too crude, and it is precisely that crudeness that led the court of appeal astray.
The main rule: not "who asserts", but "who invokes"
The allocation of the burden of proof is governed by Section 150 DCCP: the party that invokes the legal effects of facts or rights asserted by it bears the burden of proving those facts or rights, unless a special rule or the requirements of reasonableness and fairness dictate a different allocation. A deed does not shift that main rule: conclusive evidential force brings no reversal of the burden of proof, and once the evidence to the contrary succeeds, the claimant is thrown back on Section 150 DCCP. The adage "he who asserts must prove" captures only the ordinary case: usually it is the claimant who invokes a legal effect. The law, however, looks not to the procedural role but to the substantive position. What is decisive is who invokes the legal effect of asserted facts, and that may equally be the defendant.
The sequence matters too. A court reaches the taking of evidence only after a party has sufficiently stated its case and the opposing party has sufficiently and reasonedly denied it. The burden of allegation precedes the burden of proof; anyone who conflates the two also allocates the burden of proof impurely.
The pivot: a denial or an affirmative defence
A defendant may defend itself in two ways, with opposite consequences for the burden of proof.
With a reasoned denial, also called a defence on the basis of the claim, the defendant denies a fact that the claimant places at the foundation of its claim. That does not shift the burden of proof. The claimant remains burdened, however emphatic the denial. It does hold that the denial must be sufficiently reasoned, since an asserted fact otherwise becomes established.
With an affirmative or independent defence, the defendant invokes a legal effect that stands apart from the foundation of the claim but blocks its allowance. Payment, prescription, discharge and suspension are the classic examples. Because the defendant invokes that independent legal effect, it bears the burden of proving it. That is still the main rule of Section 150 DCCP, now applied to the defendant.
The temptation is to capture the distinction in the formulas "no, because" for the denial and "yes, but" for the affirmative defence. Those formulas do not hold, as the Advocate-General stresses in his opinion preceding the gold case (ECLI:NL:PHR:2026:449, paras. 3.9-3.11, referring to Ahsmann). Nearly every defence can be cast in either form. "Yes, I had the gold, but I left it behind" and "no, I do not have the gold, because I left it behind" express the same thing. What is decisive is not the wording, but whether the legal effect invoked stands apart from the foundation of the claim.
The gold case: a denial, not an affirmative defence
The case thus unravels. The wife claims delivery of half of the gold, and under Section 150 DCCP she must state and, if necessary, prove that the husband has the gold (ECLI:NL:HR:2026:1292, para. 3.2). The husband's defence, that he left the gold behind in the home, is not an invocation of an independent legal effect standing apart from that foundation. It is a denial of the very fact the wife must prove, namely that the husband has the gold. That is a denial, not an affirmative defence (ECLI:NL:PHR:2026:449, para. 3.11). The court of appeal treated it as an affirmative defence and placed the burden of proof on the husband; that reflects an incorrect view of the law. The Supreme Court quashes and remits.
One nuance sharpens the picture. Had the husband advanced the same contention in support of his own counter-request, for he too claimed half of the gold, then as the party making that request he would indeed bear the burden of proving it. The appeal decision, however, was not framed in that way (ECLI:NL:PHR:2026:449, para. 3.13). The same contention, a different procedural function, a different burden of proof. That illustrates why "who asserts" is an inadequate criterion: what matters is the legal effect a party invokes, not its place in the proceedings.
The same in commercial practice: one judgment, both poles
The gold case is a family matter, but the rule is general and recurs in commercial disputes. A telling example is a case on the professional liability of a lawyer (ECLI:NL:HR:2020:1308). The lawyer had allowed a claim to become time-barred; the client sought damages under Section 6:74 DCC. For the causal connection and the loss, the client bore the burden of proof under the main rule of Section 150 DCCP. The lawyers contended that a judgment against the liable party would in any event have been unrecoverable. The court of appeal saw in this an independent defence and placed the burden of proof on the lawyers. The Supreme Court corrected this: that argument is a denial of the causal connection, not an independent defence, so that the court of appeal's ruling reflects an incorrect view of the law (para. 3.2).
The same case also shows the other pole. The lawyers' reliance on the client's duty to mitigate her loss, that she ought to have rebuilt the destroyed premises sooner (Section 6:101 DCC), is indeed an independent defence. The burden of allegation and proof of it rest on the lawyers (para. 3.4). One judgment, two defences, two outcomes. That is precisely what the rule of thumb "he who asserts must prove" fails to capture.
The practical lesson
The characterisation of the defence is decisive, and it is easily made wrongly. Before a defence is advanced, one question repays the effort: does what is put forward stand apart from the foundation of the claim, so that it invokes an independent legal effect, or is a fact denied that the claimant must prove? In the first case the burden of proof rests on the defendant, in the second the claimant remains burdened. A denial presented as an affirmative defence needlessly loads a burden of proof onto one's own shoulders; an affirmative defence dismissed as a mere denial wrongly escapes one.
Equally important is the allegation stage that precedes it. Setting the bar for a party's burden of allegation too high is itself a ground for cassation, as the Supreme Court expressly indicated in the lawyers' case (ECLI:NL:HR:2020:1308, para. 3.4). A party who characterises its assertions and its defence sharply thereby determines not only who must prove, but often also the outcome.
Frequently asked questions
What exactly does "he who asserts must prove" mean?
It is a rule of thumb for Section 150 DCCP, and it is too crude. The law looks not to the procedural role of claimant or defendant, but to who invokes the legal effect of asserted facts. Usually that is the claimant, but with an affirmative defence it is the defendant. Anyone who relies on the adage overlooks that difference.
Does the burden of proof shift if I reasonedly deny the allegation?
No. A reasoned denial does not shift the burden of proof; the claimant remains burdened with proving the facts it places at the foundation of its claim. The denial must, however, be sufficiently reasoned, since the asserted fact otherwise becomes established.
When does the defendant bear the burden of proof?
With an affirmative or independent defence: an invocation of a legal effect that stands apart from the foundation of the claim but blocks its allowance, such as payment, prescription, discharge or the duty to mitigate. Because the defendant invokes that independent legal effect, the burden of proving it rests on the defendant.
What is the difference between a defence on the basis of the claim and an affirmative defence?
A defence on the basis of the claim denies a fact the claimant must prove, and does not shift the burden of proof. An affirmative defence invokes an independent legal effect that blocks allowance, and moves the burden of proof to the defendant. The "no, because" and "yes, but" formulas are unreliable here; what is decisive is whether the legal effect invoked stands apart from the foundation of the claim.
Cited case law
Supreme Court
- ECLI:NL:HR:2026:1292: the denial of a fact placed at the foundation of the claim does not shift the burden of proof; the court of appeal wrongly treated it as an affirmative defence
- ECLI:NL:HR:2020:1308: unrecoverability is a denial of the causal connection (not an independent defence); reliance on the duty to mitigate (Section 6:101 DCC) is indeed an independent defence, with the burden of proof on the defendant
Parket bij de Hoge Raad (Advocate-General)
- ECLI:NL:PHR:2026:449: distinction between a defence on the basis of the claim and an affirmative defence; the "no, because / yes, but" formulas are unreliable, what is decisive is whether the legal effect stands apart from the foundation
See also
- Conclusive evidential force: what does a deed prove? Section 150 DCCP allocates the burden of proof; Section 157 DCCP governs the evidential force of what is then adduced.
- Commercial litigation: the broader overview
- Shareholder disputes: disputes between shareholders and the route to court