Opposing granted patents, invalidity actions and defending against infringement claims.

A granted patent is not necessarily a valid one. The Office examines on the documents it finds, and the closest prior art is often held by the people actually working in the field. Patent systems are therefore built to allow granted rights to be challenged afterwards.

This page addresses both directions: acting against someone else’s patent, and defending an infringement claim brought against you. In practice these are usually two sides of one file — the strongest answer available to an accused party is often that the patent is invalid.

Post-grant opposition

Once a grant is published in the Bulletin, third parties may oppose before the Office within the statutory period, on grounds showing the patent should not have been granted:

Lack of novelty — a document, product or use made available to the public before the filing date.
Lack of inventive step — the invention being obvious to a person skilled in the art.
Insufficient disclosure — the description not enabling a skilled person to carry out the invention.
Added matter — claims extending beyond the content of the application as filed.
Excluded subject matter — discoveries, business methods and software without technical effect.

The administrative route is faster and cheaper than court proceedings. The first benefit of monitoring competitor patents is simply not missing this window.

Invalidity proceedings

Where the opposition period has passed or opposition failed, invalidity is sought before the court. A finding of invalidity is retroactive as a rule: the patent is treated as never granted, which affects not only the future but infringement actions already brought on it.

The strength of the case turns on the quality of the prior art produced. Finding a document the Office did not see — in non-patent literature, a foreign-language publication or an expired patent — can decide the case on its own. The first step is therefore technical rather than legal: a validity search.

Invalidity need not cover the whole patent. Some claims can fall while others survive, and partial invalidity is often enough to narrow an infringement claim out of relevance.

If you are accused of infringing

The first instinct of a company receiving a patent letter is usually to halt production. That is generally unnecessary and always premature. The defence lines to work through are:

No infringement. Your product may not carry every feature of the independent claim. Partial similarity is not enough: each claim element must be present. The comparison is made element by element.
The patent is invalid. Where prior art exists that would bring the patent down, the defence attacks the right itself. This is the only defence that removes the claim entirely.
The right is not in force. The patent may have expired, annuities may be unpaid, or it may never have been validated in Türkiye. See patent annuity fees.
Prior user right. Someone who in good faith began using the invention, or made serious preparations to do so, before the filing date may continue on a limited basis. This defence stands or falls on dated records.
Exhaustion. Where the product was put on the market by the proprietor or with their consent, subsequent sales cannot as a rule be blocked. See exhaustion and parallel imports.
Licence or design-around. A commercial answer sits alongside the legal ones: take a licence, or redesign the product to fall outside the claim.

Enforcing your own patent

The tools resemble those in trademark disputes, but the technical burden of proof is far heavier. Infringement is shown by mapping the claim onto the product element by element, which usually requires expert evidence.

Cease-and-desist letter — one containing the element-by-element mapping generally opens negotiations.
Preliminary injunction — halting manufacture or import, on prima facie proof of technical infringement.
Actions for determination, cessation and prevention, with damages.
Customs seizure — surveillance applications for imported goods.
Preservation of evidence, where infringement is by nature ephemeral.

Assume from the outset that the other side will counter with invalidity. Stress-testing your own patent before suing is an inseparable part of the litigation strategy.

An earlier intervention: third-party observations

Once an application publishes at eighteen months, it is open to third-party observations. At that point, before any grant, documents showing the invention is not patentable can be put before the Office. This route costs far less than opposition or invalidity and can narrow a competitor’s file at the outset.

The reason it goes unused is simply information: nobody is watching competitor publications, so the window closes unnoticed. Monitoring a competitor portfolio is the cheapest and least practised part of a patent strategy.

Three reasons to watch competitor portfolios

Early intervention. The observation and post-grant opposition windows are not missed — both far cheaper than litigation.
Direction. Seeing which technical direction a competitor is pursuing, where they seek protection and where they abandon it feeds straight into your own R&D decisions.
Mapping free space. Patents that lapse for unpaid annuities or reach the end of their term become free to use. That knowledge lowers development cost directly.

The first thirty days after a letter

The answer to a patent letter comes from a sequence of work, not from haste or silence. In practice: first check whether the right is in force in Türkiye; then map the claims onto your product element by element; start a validity search in parallel; and finally weigh the commercial options — a licence, a design change, removing the relevant feature — against the legal ones.

An undertaking given or a payment made before that work is complete cannot be undone. Silence is equally unavailable, however: time runs and damages accumulate.

Frequently asked questions

I received a patent letter — should I stop production?

Not immediately. First compare the claims against the product and examine the patent’s validity. Ignoring the letter is equally wrong, however: silence can be read against you on bad faith and affects the damages assessment.

How long do invalidity proceedings take?

Usually several years, because expert examination is required. Where an administrative opposition window is still open, that route is considered first.

Is a foreign patent effective in Türkiye?

Not by itself. Foreign patents, European patents included, take effect in Türkiye only if properly validated. One of the first things to check on receiving a letter is whether the right is actually in force here.

Can a utility model be challenged?

Yes. Inventive step is not required, but novelty is, and a utility model failing that test can be invalidated. Because examination is lighter, utility models are more exposed to invalidity than patents.

Who can bring an invalidity action?

Anyone with a legitimate interest. The party accused of infringing is the typical claimant, but a business active in the field and kept out of the market by the patent also qualifies. The action is brought against the proprietor, and the person recorded in the register must be named.

If the patent is invalidated, can I recover licence fees paid?

Invalidity is retroactive as a rule, but that does not mean every completed contractual relationship performed in good faith unwinds. The outcome depends on the licence terms and the period the payment relates to — which is why licence agreements should contain a clause addressing invalidity.

If you have received a letter, or a competitor’s patent is blocking you, get in touch — the first step is a technical validity search.

This page is general information and does not constitute legal advice. Opposition and litigation deadlines vary; if you have received a letter, seek an assessment without delay.