The judgment of the Bundesgerichtshof (BGH, Federal Court of Justice) dated 11 March 2026 (case no. XII ZR 51/25) addresses the validity of standard-form value maintenance clauses in commercial leases. The central issue is whether a rent adjustment linked to the Consumer Price Index is subject not only to the requirements of the Preisklauselgesetz (PrKG, German Price Clause Act), but also to a review of its substance under §§ 305 et seq. BGB (German Civil Code), and what legal consequences arise if such a clause is invalid.
The BGH makes it clear that an indexation clause agreed in a standard-form contract must comply both with the requirements of the Preisklauselgesetz and with the substantive review applicable to standard terms and conditions. If the clause violates the requirements of § 307 BGB, it is invalid from the outset. This may give rise to substantial repayment claims by the tenant in respect of rent increases already paid.
Lease with a Standard-Form Value Maintenance Clause
The judgment arose from a legal dispute between the landlord and the tenant of commercial premises. On 28 August 2019, the parties entered into a commercial lease for premises to be used as a physiotherapy practice. The lease commenced on 1 September 2019 and had a minimum term of ten years.
In § 6, the lease contained a standard-form value maintenance clause. Under this clause, the agreed rent was initially to remain unchanged for a period of 24 months, i.e. until 31 August 2021. Thereafter, the rent was to change in line with the Consumer Price Index (CPI) published by the Statistisches Bundesamt (Federal Statistical Office).
However, the agreed base value for the index-linked adjustment was not the commencement of the lease in September 2019, but the Consumer Price Index already published in May 2017.
The clause further provided that, in the event of a change in the Consumer Price Index, the rent would automatically be adjusted by the same proportion. However, the change was to take effect only from the month following the change in the index and after written notice from the landlord.
Doubts About the Validity of the Value Maintenance Clause
From April 2022, the landlord demanded a rent increase on the basis of this provision. The tenant initially complied with the demand for an increase. However, when the landlord asserted a further rent increase, the tenant challenged the validity of the value maintenance clause.
She argued that the clause was invalid as a standard term and demanded repayment of the additional amounts already paid as a result of the indexation. Further payments were made subject to a reservation of the right to reclaim them.
Claim Successful Before the Lower Courts
In its judgment dated 23 October 2024 (case no. 5 O 23/24), the Landgericht Düsseldorf (Düsseldorf Regional Court) upheld the tenant’s claim. It found that the value maintenance clause had been invalid from the outset and ordered the landlord to repay EUR 6,498.90 plus interest and to reimburse pre-litigation legal fees.
The Oberlandesgericht Düsseldorf (Düsseldorf Higher Regional Court) upheld this decision in its judgment dated 5 June 2025 (case no. I-10 U 146/24).
The landlord appealed this decision on points of law to the Bundesgerichtshof.
BGH Dismisses Appeal on Points of Law
The Bundesgerichtshof dismissed the landlord’s appeal on points of law. It thereby upheld the decision of the Oberlandesgericht Düsseldorf and confirmed that the agreed value maintenance clause was invalid.
The key findings of the judgment can be summarised in two guiding principles:
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First guiding principle: An indexation clause contained in the standard terms and conditions of a commercial lease is subject not only to the restrictions imposed by the Preisklauselgesetz, but also to the substantive review applicable to standard terms and conditions.
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Second guiding principle: If such a clause fails the substantive review applicable to standard terms and conditions, the legal consequences are not governed by § 8 PrKG. Instead, the clause is invalid from the outset (ex tunc) pursuant to § 307(1) BGB.
The BGH thus expressly clarifies that the Preisklauselgesetz does not preclude the application of the statutory provisions governing standard terms and conditions.
For the clause at issue, this meant that it did not become invalid for the future only upon a final and binding judicial determination. Rather, because it was incompatible with § 307 BGB, it had no legal effect from the time the contract was concluded.
The landlord was therefore not entitled to demand the rent increases made on the basis of this clause.
Additional Substantive Review Alongside the Preisklauselgesetz
The BGH’s decision is based primarily on the relationship between the Preisklauselgesetz and the substantive review of standard terms and conditions under § 307 BGB.
First, the BGH had to address whether value maintenance clauses in commercial leases are to be assessed exclusively under the Preisklauselgesetz or whether they are also subject to a separate review under §§ 305 et seq. BGB.
Preisklauselgesetz Governs the Permissibility of Price Clauses
The Preisklauselgesetz governs the permissibility of price clauses, particularly agreements under which the amount of a monetary obligation is linked to changes in a specific price index.
§ 8 PrKG contains a special provision concerning the legal consequences of invalid price clauses. Under that provision, invalidity generally takes effect prospectively only once the statutory violation has been established by a final and binding judgment.
However, the BGH makes it clear that this statutory provision does not displace the substantive review applicable to standard terms and conditions.
The two regulatory frameworks pursue different objectives:
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The Preisklauselgesetz is intended in particular to counteract inflationary developments and protect the stability of the monetary system.
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The substantive review applicable to standard terms and conditions is intended to prevent one contracting party from being unreasonably disadvantaged by pre-formulated contractual terms.
A clause may therefore satisfy the requirements of the Preisklauselgesetz and nevertheless be invalid under § 307 BGB because it unreasonably disadvantages the other contracting party.
The BGH thus confirms that the two standards of review must be applied independently of one another.
Unreasonable Disadvantage Due to the Selected Index Base Value
In the specific case, the BGH found that the tenant was unreasonably disadvantaged because the Consumer Price Index for May 2017 had been agreed as the starting point for calculating the rent adjustment.
However, the lease was not concluded until August 2019 and commenced on 1 September 2019.
By selecting the index level from May 2017, the subsequent rent adjustment also took account of inflation between May 2017 and the commencement of the lease in September 2019.
As a result, the tenant was economically required to bear a rent increase based on price developments that had already occurred before the lease commenced.
During that period, the landlord had not yet provided any consideration in the form of making the commercial premises available.
The BGH considered this to constitute an unreasonable disadvantage to the tenant within the meaning of § 307(1), sentence 1 BGB.
The decisive factor was therefore not merely the general permissibility of index-linked rent, but the specific drafting of the contractual adjustment mechanism.
Breach of the Transparency Requirement
In addition, the BGH objected to the lack of transparency in the value maintenance clause.
Under § 307(1), sentence 2 BGB, standard terms and conditions must be drafted clearly and comprehensibly. The contracting party must be able to identify the rights and obligations arising from the relevant provision.
In this respect, the clause at issue contained contradictory provisions:
On the one hand, it stipulated that the rent would automatically change by the same proportion if the Consumer Price Index changed.
On the other hand, it provided that the rent adjustment would take effect only from the month following the change in the index and after written notice from the landlord.
It was therefore not sufficiently clear to the tenant whether the rent adjustment actually took effect automatically or whether an additional declaration by the landlord was required.
This contradictory drafting breached the transparency requirement under § 307(1), sentence 2 BGB.
The invalidity of the clause was therefore based on two independent grounds, each of which was sufficient in itself: the unreasonable disadvantage to the tenant under § 307(1), sentence 1 BGB and the breach of the transparency requirement under § 307(1), sentence 2 BGB.
Invalidity from the Outset
The legal classification of the invalidity is of particular significance.
The BGH had to decide whether the invalidity of the clause under § 8 PrKG took effect only prospectively or whether the clause was invalid from the outset due to the violation of § 307 BGB.
The BGH adopted the latter position.
In its view, a distinction must be made between two different scenarios:
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First scenario: A price clause violates only the Preisklauselgesetz. In this case, the legal consequence is governed by § 8 PrKG. As a general rule, invalidity takes effect prospectively only upon a final and binding judicial determination.
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Second scenario: A price clause additionally fails the substantive review applicable to standard terms and conditions. In this case, the legal consequence is governed by § 307 BGB. The clause is invalid from the outset.
The BGH thus expressly distinguishes this case from the case law concerning the special provision on legal consequences in § 8 PrKG and makes it clear that this provision cannot be applied to a separate finding of invalidity under § 307 BGB.
Consequently, the value maintenance clause at issue had already been invalid since the lease was concluded.
As the landlord had received the increased rent payments without a valid contractual basis, they had to be repaid.
Legal Consequences of the Judgment
The judgment is of considerable practical significance for the drafting and review of commercial leases.
In particular, it has the following consequences:
Twofold Validity Review of Indexation Clauses
In future, value maintenance clauses in commercial leases must not only comply with the requirements of the Preisklauselgesetz, but must also pass a separate substantive review under the law governing standard terms and conditions.
Mere compliance with the Preisklauselgesetz is therefore insufficient to ensure the validity of a standard-form indexation clause.
When drafting contracts, landlords must pay particular attention to ensuring that the agreed indexation does not unreasonably disadvantage the tenant and that the provision is sufficiently transparent.
For contractual practice, it is therefore advisable to select as the base value for indexation the index level corresponding to the date on which the contract is concluded or the lease commences, and to state this reference point expressly. According to the official text of the BGH judgment, the case decided specified a base value from September 2019 of 100% = EUR 1,748.00 net rent excluding service charges, while linking the index to its May 2017 level—this very disconnect was the basis for the objection. It should also be stipulated unequivocally whether the adjustment takes effect automatically or requires a declaration; both options are permissible, but combining them is not.
Increased Risk of Repayment Claims for Landlords
The consequences for rent increases already implemented are particularly far-reaching.
If a standard-form value maintenance clause is invalid because it violates § 307 BGB, it does not merely cease to have effect from the date of a final and binding judicial decision; rather, it has no effect from the time the contract was concluded.
Tenants may therefore generally also reclaim amounts already paid as increases.
The legal basis for this is generally the restitution claim based on unjust enrichment under § 812(1), sentence 1, alternative 2 BGB.
This requires the payment to have been made without legal grounds and there to be no other valid contractual basis for the increased rent.
In the case decided, this resulted in a repayment claim by the tenant in the amount of EUR 6,498.90 plus interest and pre-litigation legal fees.
Review of Existing Commercial Leases
The judgment provides grounds for reviewing existing commercial leases to determine whether their value maintenance clauses are valid.
This applies in particular to longer-term leases under which rent adjustments are linked to the Consumer Price Index.
Significance for Ongoing and Terminated Leases
The decision is relevant not only to the drafting of future contracts.
Since a clause that is invalid under § 307 BGB is invalid from the outset, past rent increases may also be affected.
In principle, this also applies where the corresponding payments have already been made over an extended period.
However, the applicable limitation rules must be observed when enforcing repayment claims. In particular, the standard three-year limitation period under §§ 195, 199 BGB must be taken into account. Depending on the individual case, further issues may also be relevant, including knowledge of the repayment claim, limitation and possible forfeiture.
The judgment therefore does not establish a general right to repayment of all index-linked rent increases ever paid.
Not All Indexation Clauses Are Automatically Invalid
However, it is important not to overstate the scope of the decision.
The BGH did not rule that all value maintenance clauses in commercial leases are invalid.
Rather, the decision concerns standard-form indexation clauses that are subject to substantive review under the law governing standard terms and conditions and fail that review.
An individually negotiated contractual provision must generally be assessed differently, as it is not automatically subject to substantive review under § 307 BGB. However, the other statutory validity requirements, particularly those of the Preisklauselgesetz, continue to apply. The specific drafting of the contractual provision in question is therefore always decisive.
Conclusion
In its judgment dated 11 March 2026 (case no. XII ZR 51/25), the Bundesgerichtshof further clarified the requirements governing the validity of standard-form value maintenance clauses in commercial leases.
The key finding of the decision is that indexation clauses are not to be assessed exclusively under the Preisklauselgesetz. Rather, they are additionally subject to substantive review under the law governing standard terms and conditions pursuant to § 307 BGB.
MTR Legal advises landlords and tenants on the legal assessment of rent increases, indexation clauses, payment arrears, lease terminations and eviction proceedings. Further information is available at legal advice on real estate law.
