How to Learn Whether a Patent Already Exists for an Invention

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When a patent already exists for an invention, it means essentially that no one else can bring this concept to market during the patent time period. Since innovative thinking in many areas of industry tends to head in similar directions, the occurrence of patent infringement is a common one. That's why it's critical you do a thorough check on existing patents before you apply for one. The entire process usually takes from 1 to several weeks. Follow these steps to start your research.

Search the U.S. and European patent databases for ideas similar to yours (see the Resources section below). Many developers and inventors do this search before they embark on the development process.

Make a list of key terms associated with your potential invention. These words could describe the invention's purpose, use or composition.

Search the U.S. and European databases for these terms. In the U.S. Patent Classification Index, look up these key words to locate the classes and subclasses that might apply to your invention.

Review the Classification Schedule to double-check the pertinence of these different classes and subclasses. You can find this schedule in the Manual of Classification (see Resources below). Peruse the Classification Definitions to identify the range of the subclasses and carefully read any additional references.

Browse the appropriate classes and subclasses in the Issued Patents and the Published Applications databases (see Resources below). Search according to "Current U.S. Classification" or "CCL."

Access the full-text patents and published applications of any inventions that seem similar to your own. Carefully read through the patent's or application's claims to ensure infringement will not be an issue. If the claims match those of your potential invention, infringement is likely.

Contact a patent attorney if your idea or invention has passed your own Internet search. Ask your attorney to determine both the patentability of your idea or invention as well as potential infringement issues. This serves as your final due diligence in determining if a patent already exists for your invention.


  • To have a patent attorney do an "opinion of infringement" will cost money, but as a diligent legal measure, it could ultimately save you many headaches and dollars down the line.
  • Do not hire a "patent promotion" organization to "run with your idea." Often, those with great ideas don't have the time or will to do the necessary background research to determine if a patent already exists for the concept. The Federal Trade Commission, however, has found that many patent promotion organizations will simply steal a good idea rather than check on patents for it. And since there is, in theory, no patent on the idea, the real inventor cannot legally prove any wrongdoing.


  • To keep your costs down, use the Internet to check if a patent already exists before you call an attorney. Start with the U.S. Patent and Trademark Office to do a patent search on patents dating all the way back to 1790. The European patent database includes both European and U.S. patents dating back 80 years.