Value-protection clause void? When commercial tenants can reclaim overpaid rent (BGH 2026)

Does your commercial rent rise automatically every year in line with the consumer price index? Then your lease contains a value-protection or index clause. A March 2026 ruling by Germany's Federal Court of Justice (BGH) has noticeably improved the position of commercial tenants — and so far it is discussed almost exclusively from the landlord's side. This article explains it from the tenant's perspective: general information, not legal advice.

What the BGH decided

On 11 March 2026 (case no. XII ZR 51/25), the Federal Court of Justice settled a long-open question in favour of commercial tenants: a standard-form index or value-protection clause in a commercial lease is subject not only to the Price Clause Act (Preisklauselgesetz) but additionally to the fairness review of standard terms under § 307 BGB.^1,2

The decisive point is the legal consequence. Until now, landlords could argue that a flawed price clause only falls away under § 8 PrKG once a breach has been finally established, and only for the future (ex nunc) — until then it counts as "provisionally valid".³ The BGH now makes clear: if the clause fails the fairness review, it is "void ex tunc under § 307(1) BGB" — that is, from the outset.¹ That removes the legal basis for increases already paid. For you as a tenant, this shifts the perspective: it is no longer only about future rent, but potentially about amounts overpaid in the past.

The specific flaw in the decided case

The case concerned the premises of a physiotherapy practice (contract dated 28 August 2019, tenancy starting 1 September 2019). The clause tied the rent to the consumer price index — but the agreed baseline was the index level of May 2017, more than two years before the tenancy began.¹

The BGH saw this as an unreasonable disadvantage under § 307(1) sentence 1 BGB: the inflation that accrued between May 2017 and September 2019 fell on the tenant "even though she received no consideration during that period".^1,2 There was also a transparency breach (§ 307(1) sentence 2 BGB): the clause promised an "automatic" rent adjustment on the one hand, yet made it dependent on a "written request by the landlord" on the other — a contradiction that did not make clear when and how the rent would change.¹

How to spot a problematic clause yourself

Two warning signs from the ruling can be applied to your own contract:

Both are indicators, not certainties — the legal assessment depends on the exact wording of your clause.¹ boomerent analyses your specific value-protection clause for exactly these patterns and surfaces anything unusual; whether claims follow from that is for a lawyer to assess in the individual case.

Reclaiming overpaid rent

Because the clause was void from the outset, the increase amounts were, per the ruling, "paid without legal grounds" — the landlord had to repay them (in the case: €6,498.90 plus interest).¹ Legally this is a claim in unjust enrichment (§§ 812 ff. BGB); the judgment itself does not cite these sections by number, but the classification is well established.^4,7

Important — and often misunderstood: the ruling says nothing about limitation. In general, enrichment claims are subject to the standard three-year limitation period (§ 195 BGB). It does not run from the day of payment; under § 199(1) BGB it begins only at the end of the year in which the claim arose and you became aware of the relevant circumstances.^5,6 How far a reclaim actually reaches is a question of the individual case.

Does this also apply to residential housing? And what about "Mietrecht II"?

Commercial tenants are governed by the Price Clause Act, not the residential provisions of §§ 557a/557b BGB. The BGH expressly notes that § 1(3) PrKG leaves the index rent under § 557b BGB (residential) "unaffected" — the two regimes are separate.¹

Relevant to the current debate: the planned index-rent cap in the "Mietrecht II" draft act (BT-Drs. 21/6807, first Bundestag reading on 9 July 2026) applies only to residential housing in tight markets; as of August 2026 it has not been enacted.⁸ For commercial rents this means: a political cap will not help you — your lever is the fairness review of your own clause under the BGH ruling.

What you can do now as a tenant

After the ruling, it is worth taking a sober look at your own commercial lease:

• Is there an index or value-protection clause at all?
• Does the agreed baseline index predate your tenancy?
• Is there a contradiction between "automatic" adjustment and a request requirement?
• Gather your previous increase letters and proof of payment.

boomerent analyses your clause and surfaces such anomalies. The legal assessment and any reclaims — including limitation questions — then belong in a lawyer's hands.¹