Debate over rent adjustment clauses still unresolved

The debate over rent adjustment clauses in private-sector tenancy agreements appeared to have been largely resolved by the end of 2024. The Supreme Court ruled at the time that an annual rent increase consisting of CPI indexation plus a surcharge of up to 3 per cent is generally not unfair. My colleague Koen Wanders had previously written an article on this subject entitled “Supreme Court delivers a definitive ruling on the controversial rent increase clauses”.

However, it appears that the final word has not yet been spoken. This is because, subsequently, in 2025, the Court of Justice of the European Union handed down two judgments that may point in the opposite direction. The subdistrict court judge at the Amsterdam District Court has therefore announced, in a judgement dated 28 April 2026, his intention to refer questions for a preliminary ruling to the Court of Justice of the European Union. These questions once again concern whether rent adjustment clauses based on the CPI plus a surcharge can be unfair.

Why these new questions matter

The case concerns tenants of self-contained accommodation in the private sector. Their rental agreements stipulated that the rent would be increased annually by the inflation rate published by Statistics Netherlands (CBS), plus a surcharge of up to 7 per cent. The clause in question also contained:

Ø an explanation of how the surcharge is determined, namely on the basis of the WOZ values of the let property;

Ø a provision stating that the rent increase applies even without separate notice of the increase; and

Ø a reservation that, in the event of hyperinflation or deflation, the landlord may at any time adjust the rent to the market rate if it deems this appropriate.

This is a remarkable clause. I have never before encountered a clause in my practice that offers landlords such flexibility to adjust the rent. The tenants therefore argue that the clause is unfair within the meaning of the European Directive on unfair terms. They consequently contend that it should be set aside, and that they are entitled to reclaim any rent overpaid. The landlord, on the other hand, argues that the clause is necessary to ensure that the rent keeps pace with cost and market developments over a longer period.

This is not merely an academic debate. If a rent adjustment clause is unfair, it could mean that past rent increases are invalid. In some cases, this may lead to claims for reimbursement or disputes over the rent still due.

The Supreme Court previously gave landlords some breathing space

On 29 November 2024, the Supreme Court ruled that the indexation clause and the surcharge clause can be assessed separately. According to the Supreme Court, an indexation clause serves a different purpose to a surcharge clause. Indexation compensates for inflation, whilst a surcharge may serve to offset other cost increases or changes in value.

Furthermore, the Supreme Court ruled that a surcharge of up to 3 per cent on top of the CPI is, in principle, not unfair. This was good news for landlords. The feared scenario in which rent increases would have to be refunded on a large scale thus appeared to have been largely averted.

However, the subdistrict court in Amsterdam is now questioning whether this approach is fully in line with EU law. Precisely because European consumer law is ultimately interpreted by the Court of Justice, the ruling from Luxembourg could have far-reaching consequences. In the judgment, the parties were given until 26 May to comment on the questions proposed by the judge. I assume, however, that the questions, as formulated in the judgment, will be put to the Court in more or less the same form. To be continued, then.

Should they be split, or assessed as a single whole?

A key question is whether a provision containing both indexation and a surcharge may simply be split into two parts. The Supreme Court previously held that it could. The subdistrict court now wishes to know whether EU law precludes this.

The subdistrict court judge also asks whether the cumulative effect of both components must be given sufficient weight. In other words: even if indexation and a surcharge are understandable in isolation, their combination may still prove too onerous for the tenant.

This point is relevant in practice. A surcharge of a few per cent may seem straightforward on paper, but it is reflected in the rent every year. Particularly over a longer tenancy period, the difference between indexation alone and indexation plus a surcharge can mount up significantly.

Transparency, termination and the housing market

The Amsterdam Subdistrict Court is also raising questions about the transparency of such clauses. Must the contract itself state why the landlord is permitted to increase the rent above the CPI? Or may the landlord explain those reasons at a later stage during legal proceedings?

The tenant’s position also plays an important role. In many tenancy agreements, the tenant is legally entitled to give notice if they do not wish to pay the higher rent. However, the magistrate’s court wonders whether this is a realistic option in a tight housing market.

That is an understandable question. Certainly for older people, tenants on a fixed income or tenants in large cities, moving house may in practice be hardly an option at all. The subdistrict court judge wants to know whether such circumstances should be taken into account when assessing whether a clause is unfair.

Take care with existing and new tenancy agreements

For landlords, this development means that caution remains advisable. The Supreme Court’s judgement provides important guidance, but certainly does not rule out further debate. In particular, clauses involving a surcharge of more than 3 per cent, unclear criteria or a provision stating that the increase applies even without separate notice deserve attention.

For tenants, this development may, on the other hand, be a reason to critically reassess existing rent increases. This applies particularly if the rent has been increased for years by the CPI plus a surcharge and it is unclear why or how that surcharge was applied.

Housing associations and professional landlords would also be well advised to review their model contracts. The debate is shifting from the question of whether a surcharge is always prohibited to whether the specific clause is sufficiently clear, balanced and verifiable.

Is this relevant to you? Give us a call

Are you, as a tenant, private landlord or housing association, dealing with a rent adjustment clause based on CPI plus a surcharge? If so, it is wise not to wait until the debate escalates further.

We would be happy to assess whether your tenancy agreement or model contract is legally sound, or whether there are grounds to challenge rent increases or, conversely, to better substantiate them. Call us without obligation, or fill in our contact form. One of our solicitors specialising in tenancy law will be happy to discuss this with you.