Publicly disclosing your invention before filing — especially outside the US

Any public disclosure before filing destroys patent rights in most countries immediately and permanently. The US has a one-year grace period: if you publicly disclose your invention (in a paper, blog post, demo, or trade show), you have 12 months to file a US patent application before that disclosure counts as prior art against you. However, most other countries — including all of Europe, China, Japan, South Korea, and Australia — have an absolute novelty requirement. Any public disclosure before filing, even 24 hours before, permanently destroys your right to patent in those countries. There is no grace period. How to avoid it: File a provisional application (or a full non-provisional) before any public disclosure. If you must disclose before filing, accept that you are trading international patent rights for the disclosure benefit. Never attend a trade show, publish a paper, or post on GitHub before filing in jurisdictions you care about.

An offer for sale more than one year before filing

In the US, offering to sell your invention (even privately) more than 12 months before filing triggers the on-sale bar and invalidates your patent. The on-sale bar (35 USC § 102(a)(1)) is a trap many inventors fall into. If your invention was 'on sale' anywhere in the world more than one year before your patent application's effective filing date, the patent is invalid — even if the sale was confidential, never completed, or just a price quote. 'On sale' was interpreted broadly in Pfaff v. Wells Electronics (1998): the invention must be the subject of a commercial offer for sale AND be ready for patenting (either physically embodied or described in sufficient detail). How to avoid it: Keep track of every sales conversation, quote, or letter of intent involving your invention. If you receive even an informal 'how much would it cost?' inquiry that you responded to with a number, note the date. File your patent application before that date plus one year. When in doubt, file earlier.

Not identifying all inventors — or listing the wrong ones

Inventorship errors — naming people who didn't invent, or omitting people who did — can render a patent unenforceable through inequitable conduct. Inventorship in patent law is a precise legal concept: an inventor is someone who conceived of at least one claim of the patent. Reduction to practice (actually building it) doesn't make you an inventor. Funding the project doesn't make you an inventor. Suggesting a problem but not the solution doesn't make you an inventor. Omitting a true inventor (deceptive omission) or adding a non-inventor (e.g. a supervisor or funder) can be inequitable conduct — a defense to patent infringement that renders the entire patent unenforceable, forever. How to avoid it: Have each claim reviewed against each potential inventor's contribution. For collaborative inventions, document who conceived what and when. Inventorship can be corrected before assertion if done without deceptive intent, but corrections made under litigation pressure look suspicious.

Describing less than your best mode of practicing the invention

Intentionally withholding your preferred embodiment — the way you actually plan to practice the invention — can render a patent invalid. 35 USC § 112(a) requires that the specification disclose the best mode known to the inventor at the time of filing for carrying out the claimed invention. This prevents inventors from filing a patent that describes an inferior version while keeping the best version as a trade secret. Post-AIA, failure to disclose the best mode is not a standalone basis for invalidity in a patent challenge, but it can still affect enforceability in some situations and is grounds for rejection during prosecution. How to avoid it: Describe your actual preferred embodiment — the way you would actually build and use the invention — in the specification. Don't describe a generic or inferior version to protect trade secrets while claiming broadly. If your preferred mode evolves between filing and grant, note it in a continuation.

Claims that aren't supported by the written description

If your claims cover more than what your specification actually describes, the patent can be invalidated for lack of written description. The written description requirement (§ 112(a)) requires that the specification 'reasonably convey to those skilled in the art that the inventor had possession' of the claimed invention as of the filing date. It is NOT enough to claim broadly if you only described one narrow embodiment. The Federal Circuit has held that a claim to a genus (broad category) can be invalid if the specification only describes a few species (specific examples) and the claim scope is not commensurate with the disclosure. How to avoid it: Review your claims against your specification before filing. For each independent claim, can you point to a written description in the specification that supports the full breadth of that claim? If you claim 'any polymer', have you described enough polymers to justify that scope? Don't broaden claims at the last minute without also broadening the specification.

Indefinite claims — scope the examiner and a court can't determine

Claims must be definite enough that a person skilled in the art can determine whether they infringe. Vague claim terms invite rejection and invalidity. The Supreme Court's Nautilus v. Biosig Instruments (2014) ruling tightened the definiteness requirement: a claim is invalid if it fails to 'inform, with reasonable certainty, those skilled in the art about the scope of the invention.' Common problem terms: 'substantially,' 'approximately,' 'high quality,' 'suitable,' and relative comparators like 'about the same size' without a defined reference point. Indefinite claims get rejected during prosecution and can be held invalid in litigation. How to avoid it: Define subjective terms in the specification — specify what 'substantially' means numerically in the context of your invention. Use functional language carefully: 'means for' language triggers means-plus-function interpretation, which limits the claim to what's described in the specification. Have a technical expert test each claim: can they determine whether a given product infringes?

Not doing a prior art search before filing

Filing without searching prior art risks building a prosecution on claims that will be rejected, and an issued patent that can be invalidated cheaply. A prior art search is not legally required before filing, but skipping it is expensive in practice. If the examiner finds prior art that anticipates your claims, prosecution can take years of argument and amendment. Worse: if the prior art existed and your attorney knew or should have known about it but didn't disclose it to the USPTO, it can be inequitable conduct. And a granted patent over known prior art can be challenged in an inter partes review (IPR) proceeding for around $35,000 — far cheaper than the patent cost you. How to avoid it: Conduct a thorough search of Google Patents, the USPTO database, academic literature (Google Scholar), and industry publications before filing. For valuable inventions, have a registered patent agent or attorney do a professional search. Disclose all known prior art to the USPTO on an Information Disclosure Statement.

Waiting too long after a public use or experimental use

Extended public testing of your invention — even calling it 'experimental' — can trigger the public use bar after 12 months. Public use of an invention more than one year before the US filing date can bar a patent under § 102(a)(1). 'Experimental use' is a narrow exception — it applies only when the use was necessary to reduce the invention to practice and was controlled (e.g. monitoring results, maintaining confidentiality). Commercial public use is never experimental. The 'experimental use' doctrine is often litigated and often lost: beta programs with real users, paying customers, or production-scale testing are typically not experimental. How to avoid it: Document any testing as experimental: maintain records showing the purpose of each test, collect technical data, and maintain confidentiality agreements with testers. If you are testing at commercial scale with real users, assume the clock is running and file before the 12-month window closes.

Filing a continuation that doesn't claim priority correctly

Errors in priority claims for continuations, divisionals, and CIPs can result in a patent with a later effective filing date — exposing it to intervening prior art. Continuation, continuation-in-part (CIP), and divisional applications claim priority back to a parent application. If the continuation contains any new matter (subject matter not in the parent), that new matter gets the continuation's filing date, not the parent's. In CIPs, claims that rely on new matter can be invalid over intervening prior art — including the parent patent itself (which is prior art after it publishes 18 months after filing). Errors in 35 USC § 120 copendency requirements can destroy the priority claim entirely. How to avoid it: Have a patent attorney verify priority chains carefully, especially in CIPs. Track which claims rely on original matter vs. new matter. When in doubt about whether matter is new, file a separate non-provisional rather than a CIP.

Mixing marketing language into the patent specification

Words like 'revolutionary,' 'superior,' and 'the best solution' in the specification can be used against you in claim construction to narrow your claims. Patent specifications are legal documents, not marketing materials. Statements made in the specification about the invention's properties, advantages, or limitations are used by courts to interpret claim scope — and can narrow claims below their literal text. A specification that says 'the invention uniquely solves X by using Y' can be read to limit claims to embodiments that use Y, even if the claims themselves don't mention Y. This is called specification disclaimer or prosecution disclaimer. How to avoid it: Write specifications in plain, technical language. Describe what the invention IS and HOW it works, not how it compares favorably to prior art (save that for the prosecution). Avoid describing any feature as essential to the invention unless it's actually claimed — or it may be read into every claim.

For Inventors

10 Things That Can Kill Your Patent Application

These mistakes have cost inventors their rights — sometimes permanently. Most are avoidable with early action and basic awareness of how patent law actually works.

Educational guide only — not legal advice. Consult a registered patent attorney for your specific situation.

FatalSeriousSignificant— risk level

#1
Publicly disclosing your invention before filing — especially outside the US
Fatal
Any public disclosure before filing destroys patent rights in most countries immediately and permanently.
The US has a one-year grace period: if you publicly disclose your invention (in a paper, blog post, demo, or trade show), you have 12 months to file a US patent application before that disclosure counts as prior art against you. However, most other countries — including all of Europe, China, Japan, South Korea, and Australia — have an absolute novelty requirement. Any public disclosure before filing, even 24 hours before, permanently destroys your right to patent in those countries. There is no grace period.
How to avoid it — File a provisional application (or a full non-provisional) before any public disclosure. If you must disclose before filing, accept that you are trading international patent rights for the disclosure benefit. Never attend a trade show, publish a paper, or post on GitHub before filing in jurisdictions you care about.
Novelty (§102) →
#2
An offer for sale more than one year before filing
Fatal
In the US, offering to sell your invention (even privately) more than 12 months before filing triggers the on-sale bar and invalidates your patent.
The on-sale bar (35 USC § 102(a)(1)) is a trap many inventors fall into. If your invention was 'on sale' anywhere in the world more than one year before your patent application's effective filing date, the patent is invalid — even if the sale was confidential, never completed, or just a price quote. 'On sale' was interpreted broadly in Pfaff v. Wells Electronics (1998): the invention must be the subject of a commercial offer for sale AND be ready for patenting (either physically embodied or described in sufficient detail).
How to avoid it — Keep track of every sales conversation, quote, or letter of intent involving your invention. If you receive even an informal 'how much would it cost?' inquiry that you responded to with a number, note the date. File your patent application before that date plus one year. When in doubt, file earlier.
Provisional vs Non-Provisional →
#3
Not identifying all inventors — or listing the wrong ones
Fatal
Inventorship errors — naming people who didn't invent, or omitting people who did — can render a patent unenforceable through inequitable conduct.
Inventorship in patent law is a precise legal concept: an inventor is someone who conceived of at least one claim of the patent. Reduction to practice (actually building it) doesn't make you an inventor. Funding the project doesn't make you an inventor. Suggesting a problem but not the solution doesn't make you an inventor. Omitting a true inventor (deceptive omission) or adding a non-inventor (e.g. a supervisor or funder) can be inequitable conduct — a defense to patent infringement that renders the entire patent unenforceable, forever.
How to avoid it — Have each claim reviewed against each potential inventor's contribution. For collaborative inventions, document who conceived what and when. Inventorship can be corrected before assertion if done without deceptive intent, but corrections made under litigation pressure look suspicious.
#4
Describing less than your best mode of practicing the invention
Serious
Intentionally withholding your preferred embodiment — the way you actually plan to practice the invention — can render a patent invalid.
35 USC § 112(a) requires that the specification disclose the best mode known to the inventor at the time of filing for carrying out the claimed invention. This prevents inventors from filing a patent that describes an inferior version while keeping the best version as a trade secret. Post-AIA, failure to disclose the best mode is not a standalone basis for invalidity in a patent challenge, but it can still affect enforceability in some situations and is grounds for rejection during prosecution.
How to avoid it — Describe your actual preferred embodiment — the way you would actually build and use the invention — in the specification. Don't describe a generic or inferior version to protect trade secrets while claiming broadly. If your preferred mode evolves between filing and grant, note it in a continuation.
#5
Claims that aren't supported by the written description
Serious
If your claims cover more than what your specification actually describes, the patent can be invalidated for lack of written description.
The written description requirement (§ 112(a)) requires that the specification 'reasonably convey to those skilled in the art that the inventor had possession' of the claimed invention as of the filing date. It is NOT enough to claim broadly if you only described one narrow embodiment. The Federal Circuit has held that a claim to a genus (broad category) can be invalid if the specification only describes a few species (specific examples) and the claim scope is not commensurate with the disclosure.
How to avoid it — Review your claims against your specification before filing. For each independent claim, can you point to a written description in the specification that supports the full breadth of that claim? If you claim 'any polymer', have you described enough polymers to justify that scope? Don't broaden claims at the last minute without also broadening the specification.
Specification (§112) →
#6
Indefinite claims — scope the examiner and a court can't determine
Serious
Claims must be definite enough that a person skilled in the art can determine whether they infringe. Vague claim terms invite rejection and invalidity.
The Supreme Court's Nautilus v. Biosig Instruments (2014) ruling tightened the definiteness requirement: a claim is invalid if it fails to 'inform, with reasonable certainty, those skilled in the art about the scope of the invention.' Common problem terms: 'substantially,' 'approximately,' 'high quality,' 'suitable,' and relative comparators like 'about the same size' without a defined reference point. Indefinite claims get rejected during prosecution and can be held invalid in litigation.
How to avoid it — Define subjective terms in the specification — specify what 'substantially' means numerically in the context of your invention. Use functional language carefully: 'means for' language triggers means-plus-function interpretation, which limits the claim to what's described in the specification. Have a technical expert test each claim: can they determine whether a given product infringes?
Specification (§112) →
#7
Not doing a prior art search before filing
Significant
Filing without searching prior art risks building a prosecution on claims that will be rejected, and an issued patent that can be invalidated cheaply.
A prior art search is not legally required before filing, but skipping it is expensive in practice. If the examiner finds prior art that anticipates your claims, prosecution can take years of argument and amendment. Worse: if the prior art existed and your attorney knew or should have known about it but didn't disclose it to the USPTO, it can be inequitable conduct. And a granted patent over known prior art can be challenged in an inter partes review (IPR) proceeding for around $35,000 — far cheaper than the patent cost you.
How to avoid it — Conduct a thorough search of Google Patents, the USPTO database, academic literature (Google Scholar), and industry publications before filing. For valuable inventions, have a registered patent agent or attorney do a professional search. Disclose all known prior art to the USPTO on an Information Disclosure Statement.
Free Patent Search →
#8
Waiting too long after a public use or experimental use
Fatal
Extended public testing of your invention — even calling it 'experimental' — can trigger the public use bar after 12 months.
Public use of an invention more than one year before the US filing date can bar a patent under § 102(a)(1). 'Experimental use' is a narrow exception — it applies only when the use was necessary to reduce the invention to practice and was controlled (e.g. monitoring results, maintaining confidentiality). Commercial public use is never experimental. The 'experimental use' doctrine is often litigated and often lost: beta programs with real users, paying customers, or production-scale testing are typically not experimental.
How to avoid it — Document any testing as experimental: maintain records showing the purpose of each test, collect technical data, and maintain confidentiality agreements with testers. If you are testing at commercial scale with real users, assume the clock is running and file before the 12-month window closes.
#9
Filing a continuation that doesn't claim priority correctly
Significant
Errors in priority claims for continuations, divisionals, and CIPs can result in a patent with a later effective filing date — exposing it to intervening prior art.
Continuation, continuation-in-part (CIP), and divisional applications claim priority back to a parent application. If the continuation contains any new matter (subject matter not in the parent), that new matter gets the continuation's filing date, not the parent's. In CIPs, claims that rely on new matter can be invalid over intervening prior art — including the parent patent itself (which is prior art after it publishes 18 months after filing). Errors in 35 USC § 120 copendency requirements can destroy the priority claim entirely.
How to avoid it — Have a patent attorney verify priority chains carefully, especially in CIPs. Track which claims rely on original matter vs. new matter. When in doubt about whether matter is new, file a separate non-provisional rather than a CIP.
#10
Mixing marketing language into the patent specification
Significant
Words like 'revolutionary,' 'superior,' and 'the best solution' in the specification can be used against you in claim construction to narrow your claims.
Patent specifications are legal documents, not marketing materials. Statements made in the specification about the invention's properties, advantages, or limitations are used by courts to interpret claim scope — and can narrow claims below their literal text. A specification that says 'the invention uniquely solves X by using Y' can be read to limit claims to embodiments that use Y, even if the claims themselves don't mention Y. This is called specification disclaimer or prosecution disclaimer.
How to avoid it — Write specifications in plain, technical language. Describe what the invention IS and HOW it works, not how it compares favorably to prior art (save that for the prosecution). Avoid describing any feature as essential to the invention unless it's actually claimed — or it may be read into every claim.
Specification (§112) →

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