USPTO kind codes are two-letter codes used by the United States Patent and Trademark Office (USPTO) to identify the kind of patent document and its publication status. These codes are appended to the patent number and help to distinguish between different types of patent documents such as utility patents, design patents, plant patents, and others, as well as their status, like whether they are published applications or granted patents.
Here's a breakdown of some common USPTO kind codes used for utility patents:
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WIPO ST.16 Kind Codes
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Kind of document
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Comments
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A1
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Patent Application Publication
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Pre-grant publication available March 2001
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A2
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Patent Application Publication (Republication)
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Pre-grant publication available March 2001
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A9
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Patent Application Publication (Corrected Publication)
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Pre-grant publication available March 2001
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B1
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Issued Patent
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No previously published pre-grant publication
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B2
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Issued Patent
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Having a previously published pre-grant publication and available March 2001
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C1, C2, C3
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Reexamination Certificate
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Previously used codes B1 and B2 are now used for granted Patents
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E
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Reissue Patent
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No change
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These kind codes are part of a broader international system used by many patent offices, known as the "kind code system," which facilitates the identification and categorization of patent documents globally.
See USPTO for additional information.