How to Bring or Defend a Patent Nullity (invalidity) Action in Greece (2026)

Patent nullity Greece proceedings are the principal route by which a granted patent can be attacked and declared invalid before the Greek civil courts, and understanding the procedure is essential for any party contemplating litigation in 2026. A nullity action seeks a declaration that a patent should never have been granted, because it lacks novelty, inventive step, industrial applicability, or fails a formal requirement, and, if successful, strips the right of legal effect. This guide sets out, in a structured and practitioner-oriented way, how the action is commenced, defended, evidenced and enforced, with indicative time spans and cost ranges.

It reflects the interplay between national procedure and the wider European patent framework, including opposition and appeal proceedings before the European Patent Office. Throughout, the emphasis is on what a litigator or in-house team actually needs to do, when, and at what approximate cost.

Overview, What is a patent nullity (invalidity) action in Greece?

A patent nullity Greece action is a civil claim seeking a judicial declaration that a granted patent is invalid, in whole or in part. In Greece the route is primarily judicial: the competent civil court examines whether the patent met the statutory conditions of patentability at the date of filing or priority. Where the claim succeeds, the court declares the patent void.

Nullity and revocation are frequently used interchangeably in practice, but they can describe distinct legal ideas. Nullity treats the patent as void from the outset, whereas revocation in some systems terminates a right prospectively. In Greece, a successful nullity declaration is generally treated as having effect from grant, meaning the patent is regarded as never having conferred valid exclusivity. This retrospective character is strategically significant: it can neutralise infringement claims and clear the field for a competitor’s freedom to operate.

The typical remedy is declaratory, the court declares the patent, or specified claims, invalid. There is no award of damages inherent in a nullity action itself, although a defendant facing a parallel infringement claim will usually raise invalidity as a defence, and a claimant may pursue nullity precisely to pre-empt or defeat an infringement threat. The practical effect of a declaration extends to the patent register and to any pending or future enforcement based on the invalidated claims.

What laws govern patent validity in Greece?

Greek patent validity is assessed against national industrial property legislation administered through the Hellenic Industrial Property Organisation (OBI), read alongside the substantive patentability standards of the European Patent Convention (EPC) where a European patent has effect in Greece. The core national framework for patents has historically been Law 1733/1987 on technology transfer, inventions and technological innovation, as amended and supplemented; practitioners should confirm the current consolidated text and any subsequent amendments before relying on specific provisions. The EPC defines the core criteria, novelty, inventive step and industrial applicability, that a Greek court will apply when testing validity. Greece is also embedded in the wider international framework through the treaties administered by the World Intellectual Property Organization.

To start a patent nullity Greece action at a high level, a claimant identifies the patent, formulates the grounds of invalidity by reference to these standards, gathers prior art and expert evidence, and files a statement of claim before the competent civil court.

Eligibility, Who can bring or defend a nullity action?

Standing to bring a nullity action is comparatively broad. Any party with a legitimate interest in the patent being declared invalid may generally commence proceedings, which typically includes competitors, alleged infringers, importers, distributors, and parties who have received a cease-and-desist demand. The defendant is ordinarily the registered proprietor of the patent, and heirs or assignees may be substituted where the right has passed.

Standing and locus standi

A claimant must demonstrate a legitimate legal interest. In practice, an alleged infringer facing enforcement, or an entity intending to launch a product covered by the patent’s claims, will readily satisfy this requirement. Parties without any commercial connection to the technical field may find their standing questioned, so the pleaded interest should be articulated clearly at the outset.

Timing and limitation issues

A nullity action attacking the validity of a granted patent may generally be brought throughout the life of the patent, reflecting the public interest in removing wrongly granted monopolies. There is little useful purpose in delaying: prior art can become harder to authenticate over time, and an early challenge can be decisive where an infringement claim is anticipated. Where the action is raised defensively within infringement proceedings, procedural deadlines governing the defence and any counterclaim will apply.

Relationship to EPO opposition and appeal

For European patents validated in Greece, an opposition before the EPO within the nine-month post-grant period is a parallel, and sometimes preferable, route to central revocation. A pending EPO opposition or appeal does not automatically bar a national nullity action, but it creates coordination questions: a Greek court may consider the EPO proceedings when case managing, and the eventual EPO outcome can affect the patent as it stands in Greece. Litigants should map both tracks before committing to either.

Step-by-step: How to invalidate a patent in Greece

The following numbered process sets out how to bring or defend a patent nullity Greece action from first review to enforcement. Each phase has a lead actor and an estimated duration; the consolidated timeline table follows. Durations are indicative and vary with court workload and case complexity.

1. Pre-filing preparation. Conduct a freedom-to-operate review, commission a professional prior-art search, and instruct a technical expert early. Identify the specific claims to be attacked and the grounds (lack of novelty, lack of inventive step, insufficient disclosure, added matter, non-patentable subject matter). Preserve documentary prior art with clear provenance. Practical tip: instruct the expert before drafting so the pleaded grounds are technically robust.
2. Filing the claim. Select the competent civil court, draft the statement of claim in Greek, and specify the relief sought, declaration of invalidity of the identified claims. Attach the patent documentation, prior art and initial supporting evidence. The filing date is day zero for procedural purposes. Practical tip: plead each ground of invalidity separately so the court can address the claims systematically.
3. Service and defence. The claim is served on the proprietor, who files pleadings and may raise procedural objections or, in a related infringement context, a counterclaim. Practical tip: anticipate the proprietor’s likely amendment or limitation of claims and prepare fallback arguments.
4. Evidence stage. Parties file written pleadings and supporting evidence, including expert reports, and produce technical documentation. This is the decisive phase in most patent nullity Greece cases because validity turns on expert analysis of the prior art against the claims. Practical tip: ensure all foreign-language prior art is accompanied by certified Greek translations to avoid admissibility challenges.
5. Hearings and judgment. The court schedules the hearing, hears the parties, and delivers a reasoned judgment in Greek. Where invalidity is established, the court declares the relevant claims void. Practical tip: prepare a concise technical primer for the bench to frame the inventive-step analysis.
6. Appeals and enforcement. Either party may appeal to the higher courts within the applicable deadline. Once final, a nullity declaration affects the register and any enforcement founded on the invalidated claims; consequential effects may be addressed in ancillary proceedings. Practical tip: factor appeal risk into any commercial decision to launch a product before the judgment is final.

Timeline: Step, Who and Duration

Required documents and form templates

The following documents represent the minimum a claimant should file and a defendant should expect to encounter in a patent nullity Greece action. Foreign-language material must be accompanied by certified Greek translations, and foreign powers of attorney will usually require apostille or equivalent legalisation. Treat the list as a filing checklist and confirm current registry requirements before filing.

Timeline and deadlines in detail

A first-instance patent nullity Greece action can take a substantial period from filing to judgment, and technically complex cases with multiple expert reports typically take longer. Because Greek civil procedure and court workloads change over time, litigants should confirm current procedural deadlines, for pleadings, defence, and evidence, against the applicable provisions of the Code of Civil Procedure and directions from the competent court rather than relying on fixed figures.

Appeals must be lodged within the applicable statutory deadline, which runs from service of the judgment (or from a later triggering event where no service is effected), and appellate determination adds further time. Practitioners should also account for the interplay with EPO timelines: the nine-month opposition window runs from mention of grant of a European patent in the European Patent Bulletin, and a pending opposition or appeal may influence the pace and case management of the national action.

To streamline proceedings, litigants can consider tightly focusing the pleaded grounds on the strongest prior art, front-loading expert evidence so it is ready at filing, and, where infringement risk is imminent, coupling the nullity strategy with an application for provisional measures. Reducing the number of contested claims and grounds often shortens the evidence phase materially.

Costs and fees, estimating litigation costs

Costs in a patent nullity Greece action vary substantially with technical complexity, the number of expert reports, and whether parallel infringement or EPO proceedings are running. The figures below are broad, indicative estimates for budgeting purposes only, not fixed tariffs; actual costs may fall outside these ranges, and court fees in particular should be confirmed with the competent registry as they depend on claim value and current rules. Complex pharmaceutical or telecoms disputes sit at the upper end.

Where the action is defensive, budgeting should also allow for coordinating with any EPO opposition, which carries its own official and representation fees (current EPO fee levels are published on the EPO website). Obtain a tailored fee estimate from Greek counsel and, where relevant, a European patent attorney before committing to a strategy.

Interim (provisional) measures and precautionary relief

Provisional measures, including preliminary injunctions, seizures and disclosure or preservation-of-evidence orders, can be sought in connection with patent disputes where urgency and a risk of irreparable harm are demonstrated. In the nullity context, provisional relief is more commonly deployed by a patentee in parallel infringement proceedings, but a party challenging validity may seek precautionary orders where its commercial position is threatened.

Obtaining urgent measures

The applicant must generally show urgency, a sufficient likelihood of success on the substantive question, and that the balance of harm favours the order. In patent matters, the court weighs the apparent strength or weakness of the patent, including any credible invalidity case, against the harm to each side. A well-evidenced argument that the patent is likely invalid can be an important factor in resisting an injunction sought by the proprietor.

Interplay with the nullity action

Provisional measures do not decide validity finally; they hold the position pending the merits. A robust patent nullity Greece case advanced at the interim stage can persuade a court to refuse or narrow an injunction, or to require the patentee to provide security. Conversely, the outcome of the nullity action can trigger the discharge of measures previously granted.

Securities and bonds

Courts may condition provisional relief on the provision of security to compensate the respondent should the measure later prove unjustified. Applicants should be prepared to fund such security, and respondents should consider requesting one where the invalidity case is strong.

What to check for 2026, legislative and case-law developments

Practitioners approaching a patent nullity Greece action in 2026 should verify the current procedural position against the promulgated texts in the Official Government Gazette and the guidance published by OBI, as periodic amendments to civil procedure and industrial property rules affect timing, admissibility and case management.

Procedural framework

Greek civil procedure places significant emphasis on front-loaded written pleadings and documentary evidence, which places a premium on having expert reports ready at or shortly after filing. Litigants who treat the evidence stage as an afterthought risk being caught by directions timetables that leave little room for late instruction of experts. Confirm the current form of the Code of Civil Procedure, which has been amended on several occasions in recent years.

Substantive law

Judicial treatment of inventive step and sufficiency of disclosure continues to be shaped by decisions of the higher courts, and by the persuasive influence of EPO Boards of Appeal reasoning on equivalent EPC criteria. Parties should check current authority through the case-law resources of Areios Pagos and, where relevant, published EPO Board of Appeal decisions when framing the grounds of a challenge.

Tactical implications

The practical effect for 2026 is that early technical investment and disciplined pleading are increasingly valuable. Coordinating national strategy with any EPO opposition, and deciding which forum leads, is a core tactical question rather than an afterthought.

Comparison: nullity (invalidity) action versus infringement proceedings

Nullity and infringement are two sides of the same coin, and litigants frequently run them together. The table below summarises the key strategic differences to help decide which lever to pull.

In many disputes a defendant to infringement will raise invalidity as a shield while also commencing or threatening a standalone nullity action as a sword. The retrospective character of a nullity declaration makes it a powerful counter to an infringement claim, because a patent held void cannot found liability.

Common pitfalls and how to avoid them

• Late expert instruction. Engaging a technical expert only after filing weakens the pleaded grounds and risks missing tight evidence deadlines. Instruct before drafting.
• Insufficient prior art. A nullity case built on marginal references rarely succeeds. Commission a professional search and identify the closest prior art before committing.
• Poor or missing translations. Foreign-language prior art and documents without certified Greek translations may be inadmissible. Budget for translation early.
• Ignoring parallel EPO proceedings. Failing to coordinate a national challenge with an EPO opposition or appeal can produce inconsistent positions and wasted cost. Map both tracks at the outset.
• Overbroad pleading. Attacking every claim on every ground dilutes focus and lengthens the evidence phase. Target the strongest claims and grounds.
• Underestimating appeal risk. Treating a first-instance win as final can lead to premature commercial decisions. Factor appellate timelines and outcomes into launch planning.

Conclusion

A patent nullity Greece action is a demanding but powerful instrument: it can clear a competitor’s blocking patent, defeat an infringement threat, and restore commercial certainty through a retrospective declaration of invalidity. Success turns on early technical investment, disciplined pleading of the strongest grounds, meticulous handling of prior art and translations, and careful coordination with any parallel EPO proceedings. Parties evaluating whether to bring or defend such an action in 2026 should verify the current procedural position against primary sources and take specialist advice before filing. For a case assessment, contact a Global Law Experts-listed Greece IP litigator.

Sources

1. Hellenic Industrial Property Organisation (OBI)
2. European Patent Office
3. World Intellectual Property Organization
4. Official Government Gazette (Ethnikó Typografío)
5. Areios Pagos (Supreme Court of Greece)
6. Athens Bar Association
7. European Commission