Written form in commercial tenancy law: what has applied to all contracts since 2026

Note: This article is for general information and does not replace individual legal advice. Questions regarding the requirement for written form in commercial lease law are highly dependent on the individual case. Have your specific contract reviewed by a lawyer.

At a glance

• Commercial leases with a term of more than one year had to comply with the written form requirement (§ 126 BGB) until the end of 2024. Since 1 January 2025, the text form (§ 126b BGB) is sufficient; since 2 January 2026, this also applies to existing contracts.
• A breach of form does not render the contract void, but makes it voidable: the contract is deemed to be for an indefinite period and is subject to standard termination.
• According to the case law of the Federal Court of Justice (BGH), clauses healing formal defects are invalid (BGH, judgment of 27.09.2017 – XII ZR 114/16).
• Defects in the written form can be remedied by an addendum in the correct form - but only with effect for the future.
• The invocation of a lack of written form is only contrary to good faith in rare exceptions (Section 242 BGB).
• The text form solves the old written form problem, but creates new risks – above all unintentional contract amendments by email.

Why the written form was explosive in commercial tenancy law for decades

To understand why this issue has caused so much economic damage, one needs to know the purpose of the norm – and how far it has strayed from its original intention.

Section 550 of the German Civil Code (BGB) stipulates that a lease agreement concluded for a period longer than one year that does not comply with the prescribed form is deemed to have been concluded for an indefinite period. Pursuant to Section 578 BGB, this provision also applies to commercial tenancies. The contract is therefore not invalid – it merely loses its fixed term. Moreover, an indefinite commercial lease agreement can be terminated in accordance with Section 580a(2) BGB no later than the third working day of a calendar quarter to the end of the next calendar quarter, by either party and without cause. In practice, this means a notice period of around six months.

Originally, Section 550 of the German Civil Code (BGB) served to protect purchasers: someone who buys a rented property automatically enters into the existing tenancy agreement by operation of law pursuant to Section 566 BGB – „purchase does not break hire“. The purchaser should be able to read reliably from the contractual document what long-term commitments they are entering into. In addition, the requirement for written form has a warning and evidentiary function: the parties are to be protected against hasty commitments, and the contents of the contract are to be provable.

In practice, however, the requirement for written form became a tactical instrument. Landlords or tenants wanting to get out of a long-term contract would have a lawyer scour the contract for formal defects. If a flaw was found – and one was almost always found – the contract could be terminated with six months' notice despite a fixed ten-year term. The Federal Court of Justice (BGH) expressly granted this right of termination to the original parties to the contract, not just to the purchaser. The result: massive legal uncertainty in long-term commercial lease agreements. An overview of the specifics of commercial lease agreements can be found in our separate contribution to commercial leases.

The eight most common written form traps – and why they will still be relevant in 2026

With the BEG IV reform, the statutory requirement for written form for commercial lease agreements has been abolished. So why still write about it? For three reasons: Firstly, many older contracts contain contractual written form clauses that go beyond the statutory standard. Secondly, written form defects in older contracts remain relevant for real estate transactions and due diligence reviews. Thirdly, according to prevailing opinion, the principles of unity of the instrument survive even under the new text form.

The following list summarises the most common defects in written form that have occurred in practice and case law over decades:

1. Oral collateral agreements regarding essential contract terms. Landlord and tenant agree with a handshake that the tenant may also use the back yard as storage space. Or that utility bills are charged at a flat rate rather than according to consumption. Such oral agreements on essential contract contents violate the written form requirement – even if the main written contract is flawless. The Regional Court of Düsseldorf ruled in one case that merely the oral agreement on the use of an area during a local shooting festival constituted a breach of the written form and made the entire contract subject to ordinary termination.
2. Attachments without sufficient reference. A commercial lease agreement refers to an attachment containing the floor plan of the rented space. The attachment exists, but is neither physically attached to the contract nor unambiguously referenced in the contract text. According to the principle of single document unity, all essential contract components must be unmistakably recognizable as belonging together. If the reference is missing, the written form requirement is breached. In one case, the Higher Regional Court of Brandenburg identified three different defects of this type in a single contract: a forgotten attachment, an unattached non-competition agreement, and an improper substitution of a party.
3. Addenda without correct reference. A second addendum refers to the main contract, but does not mention the first addendum. The Federal Court of Justice (BGH) has relaxed the requirements here (judgment of 22 April 2015 – XII ZR 55/14): simply designating it as „2nd Addendum“ can be sufficient if it follows logically that a 1st addendum exists. Nevertheless, the recommendation remains to explicitly link every addendum with all previous ones.
4. Missing or incorrect signature. In the case of a plc, only one board member signs without a representative suffix, even though joint representation applies. In the case of a partnership under civil law (GbR), not all partners sign. In the case of a GmbH, the managing director designation is missing. The Federal Court of Justice (BGH) has ruled that in the case of a plc without a representative suffix, the impression of an incomplete document is created (XII ZR 89/06). For more details, see our article on Representation for the termination of a commercial lease.
5. Retrospective modification of service charge advance payments without form. With its ruling of 14.05.2025 (XII ZR 88/23, NZM 2025, 598), the Federal Court of Justice (BGH) held: The consensual amendment of the advance service charge payments agreed in the original tenancy agreement is – regardless of its absolute or relative amount – a material contract modification that is subject to the formal requirements, at least if it applies for more than one year and cannot be revoked by the landlord at any time. The same applies to the rent amount itself: In the case of the BGH judgement of 25.11.2015 (XII ZR 114/14, NJW 2016, 311), a verbally agreed increase of just 20 euros per month was sufficient to breach the form. If such an amendment is agreed only verbally or via informal letter, the entire contractual agreement is affected.
6. Secondary areas not included in the contract. The tenant has been using the basement room beneath their retail shop and two parking spaces in the rear courtyard since the beginning of the tenancy. There is no mention of this in the tenancy agreement. If these areas are an essential part of the actual rental agreement, there is a breach of form. According to the jurisprudence of the Federal Court of Justice (BGH), ancillary areas can certainly – depending on the purpose of the tenancy – form part of the essential contractual content. How the rented area is correctly determined is explained in our article on Determination of the rental floor space in commercial lease law.

Documentary unity – the core principle and its relaxation by the BGH

The document unity principle is the core of the written form issue. The term refers to the requirement that all essential contract terms – parties, leased property, rent, term – must emerge from a single document signed by both parties. In practice, things look different: commercial lease agreements regularly consist of a main contract, attachments, addendums and supplementary agreements. If these documents are not recognisable as a single unit, the form is breached.

The Federal Court of Justice's so-called relaxation case law has gradually lowered the requirements. Since the judgment of 22.04.2015 (XII ZR 55/14), the Federal Court of Justice no longer requires a physical connection between the contractual components. A mental connection expressed through an unequivocally recognisable reference is sufficient. This means that the main contract and appendices do not have to be stapled together – but the main contract must refer to the appendices, and the appendices must recognisably refer to the main contract.

The same applies to addenda. A properly executed addendum must reference the main contract and ideally all previous addenda by explicit designation.

Is document unity surviving under the new text form? According to the prevailing view, yes. The substantive requirement—that all essential contract terms must emerge clearly and coherently from the contract documents—is independent of form. Even a contract concluded in text form must make clear which documents belong together. However, a supreme court decision on the new legal situation is still pending, and the specific requirements to be met by a uniform digital document are disputed. The risk merely shifts: instead of forgotten paper clips, there are now confusing email threads and fragmented PDF versions.

BEG IV: Text form instead of written form – the new legal situation in detail

The Fourth Bureaucracy Relief Act, with the amendment of Section 578(1) of the German Civil Code (BGB), fundamentally changed the statutory form requirement for commercial lease agreements. Consequently, Section 550 BGB is to be applied with the proviso that a lease agreement for land or premises that are not living space, which is not concluded in text form for a period longer than one year, shall be deemed to be for an indefinite period. The wording of Section 550 BGB itself remained unchanged – only its application to commercial space was amended.

What does text form according to § 126b BGB mean?

The text format is significantly more accessible than the written form. It requires a legible statement provided on a durable medium that reveals the identity of the person making the declaration. Specifically, the following suffice: emails, PDFs, scanned documents, computer faxes, and messages on electronic storage media. A handwritten signature is not required—nor is a qualified electronic signature.

Whether messenger messages like WhatsApp meet the requirements of the text form has not yet been clarified by the highest courts. The decisive factors are whether the statement is readable, can be stored permanently and can be attributed to the person making it. Anyone who wants to agree on a contract modification in a legally secure manner should not rely on this.

New contracts since 01/01/2025

For all commercial leases concluded or amended from 1 January 2025, the text form shall suffice. The written form of termination as a tactical exit strategy is excluded from the outset – provided that the text form is actually observed.

Legacy contracts: Transitional period until 01/01/2026

For commercial lease agreements concluded before 1 January 2025, a one-year transitional period applied. Up to and including 1 January 2026, these agreements could still be ordinarily terminated due to formal defects. This period has expired: since 2 January 2026, the text form requirement also applies to existing legacy contracts that remain unchanged.

However, that does not mean that every pre-existing defect is automatically waived. A prior lack of written form only loses its significance to the extent that the currently relevant text form has been observed. If the agreements in question – such as oral collateral agreements or undocumented amendments – also do not exist in text form, the defect in form remains and the contract can still be terminated ordinarily. Anyone relying on the reform should therefore first check whether the relevant agreements actually exist in a version that meets the requirements of Section 126b of the German Civil Code (BGB).

The transition period was shortened if an old contract was amended after 1 January 2025. In this case, the text form already applied from the time of the amendment.

The final wave of written-form dismissals

The year 2025 was characterised by a wave of terminations requiring written form: parties wishing to exit long-term legacy contracts used the final window of opportunity before the transitional period expired. Anyone who was aware of a defect in the written form had to act by the end of 1 January 2026 – after that, the legal basis was gone. Some of these cases are still occupying the courts today. Which deadlines, reasons and formal requirements otherwise apply to a termination are explained in our guide on Termination of the Commercial Lease Agreement.

Written form cure clauses - why the safety net has never held

For years, contract lawyers have tried to minimise the written form risk through contractual clauses. The so-called written form cure clause obliged the parties to fulfil the written form in the event of a breach of form and not to invoke the defect.

On 27 September 2017 (XII ZR 114/16, BGHZ 216, 68), the Federal Court of Justice firmly rejected this approach. Written form cure clauses are incompatible with section 550 of the German Civil Code (BGB) as mandatory law and are therefore fundamentally void. This applies regardless of whether the clause is drafted as a standard business term or as an individually negotiated agreement.

The reasoning: If a written form cure clause were effective, it would undermine the protective purpose of Section 550 of the German Civil Code (BGB) – in particular, the protection of acquirers. A property acquirer who enters into a lease agreement must be able to rely on the formal validity of the contractual document. A clause that subsequently cures formal defects would destroy this reliability. In our Contribution on the clause rectifying the lack of written form Let us present a case in which a property purchaser successfully terminated due to a defect in the written form, despite a curative clause contained in the contract.

What replaces the curing clause following BEG IV? The statutory reduction to text form makes contractual curing clauses largely redundant as far as the statutory form requirement is concerned. However, the parties can still agree on a contractual written form clause that imposes stricter requirements than the law. In this case, the contractual clause takes on the function of the old statutory written form – with new, unresolved legal consequences.

Cure of written form defects through an addendum

If a formal defect is discovered before a party terminates, it can be cured by a formally compliant addendum. The Federal Court of Justice (BGH) expressly confirmed this in a judgment dated 10.02.2021 (XII ZR 26/20). The prerequisites:

• The addendum itself must be in the proper form – under old law in writing, under new law at least in text form.
• The addendum must form a conceptual unit with the main contract through clear reference.
• The addendum must indicate that the remaining provisions of the main contract continue to apply unchanged.

However, the cure only takes effect ex nunc – from the time of the addendum, not retroactively. In the period between the formal defect and the cure, either party could have given notice of termination in the ordinary way. If notice of termination has already been given and served, a subsequent addendum is no longer of any help.

Breach of good faith pursuant to Section 242 of the German Civil Code (BGB) – when invoking a formal defect fails

In rare exceptional cases, termination on the grounds of a formal defect can be rejected as contrary to good faith. The hurdle is high: the Federal Court of Justice requires an outcome that is utterly intolerable. Case law has developed three groups of cases.

Category 1: Culpable prevention of compliance with the formal requirements

One party has intentionally or culpably prevented the other from observing the form – for instance, by acting with knowledge of the requirement for form at the time of concluding the contract, with the intention of relying on the defect later. This category of case is rare in practice because the burden of proof is difficult.

Group of cases 2: Threat to existence

The termination threatens the economic existence of the party whose contract has been terminated. The requirements are high: the Higher Regional Court (OLG) of Celle (judgment of 30.06.2023 – 2 U 27/23) and the Berlin Court of Appeal have clarified that the impending insolvency of a limited company is generally not sufficient. The endangerment of existence as a ground of bad faith is tailored to natural persons who, relying on the tenancy, have organised their existence around the use of the property – for example, a female doctor who would lose her surgery rooms and could not find equivalent rooms in the surrounding area. Our contribution on the Breach of trust due to lack of written form explains the requirements in detail.

Case group 3: Unilaterally advantageous agreement contrary to form

One party is using a subsequent contract amendment that exclusively benefits them and was not in the proper form as leverage to extricate themselves from the entire contract. On 25 November 2015 (XII ZR 114/14), the Federal Court of Justice (BGH) clarified that this conduct can constitute a breach of good faith. If, for example, a tenant has agreed a rent reduction advantageous to them in a manner that does not comply with the formal requirements and then relies precisely on this formal defect in order to terminate the contract as a whole, this is contrary to good faith.

Special case: the purchaser under § 566 BGB

The property buyer who enters into the tenancy agreement by operation of law pursuant to Section 566 of the German Civil Code (BGB) is less restricted in invoking formal defects than the original parties to the contract. The Federal Court of Justice (BGH) expressly confirmed this in a decision dated 14.05.2025 (XII ZR 88/23): If the former landlord was involved in an amendment agreement that breached the requirement of written form, the buyer can generally invoke the formal defect against the tenant even if the former landlord themselves would have been barred from doing so under the principle of good faith. Reasoning: The buyer was not involved in concluding the agreement that breached the formal requirements, and the protection of the buyer is the main purpose of the legal provision. When a buyer enters into a long-term commercial lease is shown in our article on Binding of the purchaser to the tenancy agreement.

Written form and text form in comparison

Feature	Written form (§ 126 BGB) - until 31.12.2024	Text form (§ 126b BGB) - since 01.01.2025
Signature	Hand-signed by all parties on the same document	Not required; naming the person explaining is sufficient
Medium	Original paper certificate	Any durable medium: email, PDF, scan, storage medium
Certificate unit	Required; mental association is sufficient	Still required according to prevailing opinion – requirements still unclear
Legal consequences in case of violation	Contract is deemed to be for an indefinite period and may be terminated by giving notice	Same legal consequence, Section 550 of the Civil Code (BGB) via Section 578 (1) sentence 2 of the Civil Code (BGB)
Written form clause	Invalid (BGH XII ZR 114/16)	No longer relevant for the statutory requirement for form; open in the case of contractual written form clauses
Scope	Commercial property leases for one year, until 31 December 2024	Commercial leases of over one year, since 01/01/2025; existing leases since 02/01/2026
Residential leases	Written form	No change – for living space, § 550 BGB remains unchanged; the text form requirement of § 578 BGB only applies to commercial space

The new risks under BEG IV

The reform has solved the old written form problem, but created new risks. Three of these deserve special attention.

Risk 1: Unintentional contract amendment by e-mail

Under the old legal situation, an agreement made orally or by email could certainly be materially effective, but it breached the requirement for written form – with the well-known legal consequence. The text form changes the situation: a rent increase confirmed by email, a message in which the landlord promises an expansion of space, or an exchange regarding modified service charge prepayments can now constitute a formally valid contract modification. Without a form issue, without vulnerability – but also without the parties being aware that they had just concluded a binding addendum.

This is particularly tricky in negotiations that are actually supposed to still be non-binding. Under the old written form requirement, it was clear: as long as no paper is signed, nothing is binding. This argument largely falls away under the text form requirement.

Risk 2: Contractual written form clauses in legacy contracts

Many legacy contracts contain clauses such as: „Amendments and additions to this contract must be in writing.“ What happens to such clauses after 2 January 2026?

The answer depends on whether it is a simple or a double written-form clause. A simple written-form clause can generally be amended by a priority individual agreement, including orally or in text form (Section 305b of the German Civil Code (BGB)). A double written-form clause, which also makes the amendment of the clause itself subject to the written form, is harder to circumvent, but according to the case law of the Federal Court of Justice (BGH), it can likewise be superseded by a priority individual agreement if it has the character of standard terms and conditions.

A different standard also applies to contractually agreed written form clauses than to the statutory form: Section 127(2) of the German Civil Code (BGB) is decisive, not Section 126 BGB. Case law on this matter is inconsistent. The Higher Regional Court of Munich considers WhatsApp text messages and attachments such as PDFs or photos to be suitable for maintaining a contractually agreed written form, whereas voice, audio and video files are not (judgment of 11.11.2024 – 19 U 200/24 e). The Higher Regional Court of Frankfurt assesses the issue differently (NJW 2024, 1425). For commercial lease agreements with a contractually agreed written form clause, this means that whether an amendment agreement made via messenger satisfies the clause currently depends on the court having jurisdiction.

It is important to distinguish this from the statutory form. A breach of a purely contractually agreed written form clause leads to not easily leads to the contract being deemed concluded for an indefinite period pursuant to Section 550 of the German Civil Code (BGB) and being subject to ordinary termination. This legal consequence attaches to the statutory form, not to a contractual agreement. What consequence a breach of the contractual clause has instead – invalidity of the modification agreement, priority of individual terms pursuant to Section 305b BGB, or another legal consequence – depends on the interpretation of the respective clause and has not yet been conclusively clarified. Anyone wishing to base a termination on a breach of a contractual form clause should have the clause reviewed by a lawyer in advance.

Risk 3: Due diligence in property transactions

For property buyers, checking the written form has hitherto been a standard item in every due diligence process. Under the old legal situation, the completeness of a lease agreement could be assessed relatively clearly on the basis of the physical contract document. With text form, this is becoming more difficult: contract amendments can be buried in email threads that appear neither in the data room nor in the contract folders. The completeness of the contractual documentation is therefore harder to prove.

For purchasers, this means: have the seller guarantee that all tenancy agreements have been fully disclosed – including informal side agreements and email correspondence with contractual content. For landlords: maintain a central contract file in which not only the main contract and addenda, but also all relevant emails are documented.

Checklist: How to check your commercial lease for vulnerability

These ten points will help you to identify weaknesses in your existing commercial lease agreement – regardless of whether you are a tenant, landlord or investor.

1. Was the contract concluded before or after 1 January 2025? For new contracts from 2025 onwards, text form is sufficient. For existing contracts, it has applied since 2 January 2026 – however, contractual written form clauses may continue to apply.
2. Does the contract contain a written form clause? If so: single or double clause? Standard terms or individual agreement? Does it still comply with the new law?
3. Are all investments named in the contract and clearly assigned? Missing references are the most common type of defect.
4. Are all addendums numbered consecutively and refer to the main contract and all previous amendments?
5. Were contract amendments documented in the correct form after the main contract was concluded? Oral agreements, informal correspondence and emails with no discernible contract-like character are sources of risk.
6. Have all parties signed correctly – for legal entities, all authorised representatives? For a GbR, all partners; for a PLC, with the addition of the power of representation.
7. Were operating cost prepayments increased after the contract was concluded? Any permanent increase constitutes a material contract modification and is subject to formal requirements.
8. Have option rights been exercised in due form? A simple letter could constitute a defect under old law.
9. Does the tenant use areas that are not listed in the rental agreement? Cellars, parking spaces and open areas can be essential components of the contract.
10. Is there any email correspondence that could be construed as a binding variation of contract? Search the correspondence for tenancy agreement-related commitments.

What does that mean for commercial tenants?

The possibility of getting out of a long-term legacy contract due to a lack of written form has largely ceased to apply to the statutory form requirement since 2 January 2026. However, please check whether your contract contains a contractual written form clause and whether this was breached. Alternatively, a mutually agreed termination or – if there is good cause – a cancellation without notice Consideration.

If you want to continue the contract, the reverse applies: make sure that you do not inadvertently conclude a contract modification in ongoing correspondence that you did not intend to conclude.

What does that mean for landlords?

Conduct a systematic review of your tenancy agreements using the checklist above. Remedy any discovered defects through formally correct amendments and update outdated written form clauses. And establish rules in your property management regarding how to handle tenancy-related email correspondence in order to avoid unintentional contract amendments in text form.

What does that mean for investors and purchasers?

The old formal requirement risk is reduced, but not eliminated. Contractual written form clauses, undocumented collateral agreements and fragmented email correspondence remain sources of risk. Demand full disclosure of all lease-related correspondence, not just formal addenda. And, in the case of legacy contracts, check whether formal defects in the 2025 transition phase were still used to effect terminations that are now resulting in eviction disputes.

Frequently asked questions

What happens if a commercial lease agreement does not comply with the form?

The contract is valid, but is considered to be of indefinite duration – and can be terminated by either party by giving the statutory notice period. Since 2 January 2026, this only applies to breaches of the text form or of contractual written form clauses.

Does the requirement for written form still apply to commercial leases?

The legal requirement for written form has been replaced by text form. This has applied to new contracts since 1 January 2025, and has also applied to existing contracts since 2 January 2026. However, contractual written form clauses may continue to impose stricter requirements.

What is the deed unit?

The requirement that all essential contractual terms must emerge from a single coherent document. A physical connection is not necessary, but an unambiguous intellectual reference between the main contract, annexes and addenda is.

Are written form clauses effective?

No. In a judgement dated 27 September 2017 (XII ZR 114/16), the Federal Court of Justice declared them fundamentally invalid, regardless of whether they are formulated as standard terms and conditions or as individually negotiated agreements.

Can a lack of written form be cured?

Yes, by means of a properly executed addendum that clearly refers to the main contract. However, the rectification only takes effect for the future. If the notice of termination has already been received, the addendum is no longer of any help.

When is invoking a formal defect contrary to good faith?

Only in exceptional cases: in the event of culpable prevention of compliance with the form, if the existence of natural persons is endangered, or if one party uses a non-conforming agreement that is unilaterally advantageous to them as a lever for termination.

Can a limited liability company claim that its existence is jeopardised?

As a general rule, no. The Berlin Court of Appeal and the Higher Regional Court of Celle have ruled that the imminent insolvency of a limited company is not sufficient for it to be deemed contrary to good faith.

Is an email sufficient for a commercial lease?

Yes for the statutory formality requirement, provided the statement is legible, can be stored permanently and allows the person making the statement to be identified. All essential contract terms must be recognisable in a coherent manner. If the contract contains a contractual written form clause, a stricter standard may apply.

When you need legal advice

For decades, the requirement for written form in commercial tenancy law was the technically most complicated source of error in German tenancy law. The BEG IV reform has simplified the situation, but has not answered all questions. Contractual written form clauses, the interplay between old and new law, open questions regarding the unity of documents under text form, and the risk of unintentional conclusion of contracts by email continue to create a need for legal advice.

Whether you want to have an existing contract checked for vulnerability, defend yourself against a notice of termination in writing, or need to adapt your contract landscape to the text form: we will check your contract and tell you where you stand.

Important Note: The content of this article has been prepared to the best of our knowledge and belief. However, due to the complexity and constant evolution of the subject matter, we must exclude liability and warranty. The content of this article has been compiled to the best of our knowledge and belief. However, the complexity and constant changes in the subject matter make it necessary to exclude liability and warranties. If you require legal advice, please call us without obligation on 0221 – 80187670 or send us an email at info@mth-partner.de.