Have you ever wondered what those letters and numbers are at the end of a published patent application or issued patent number? The number and/or letter are collectively known as kind codes. The kind code associated with a published patent document describes the type of document and the stage of prosecution when the document was published.

U.S. patent documents are identified by a number (shown on the face of the document) that includes the following three elements:

  1. the two-character country code (US for United States of America);
  2. the patent or publication number; and
  3. the kind code as per the World Intellectual Property Organization (WIPO) Standard St.16, which has been in use by the USPTO since January 2, 2001.

For example, U.S. Patent No. 7,654,321 will be represented on the face of the patent as “US 7,654,321 B1” according to the above scheme. Similarly, U.S. Patent Application Publication No. 2003/1234567 will be represented by the number “US 2003/1234567 A1” on the face of the publication. For published patent applications, note that the first 4-digit number represents the year the application was published. Each year the numbering of published patent applications begins again with the new four digit year (e.g., 2016) and the number 0000001, so the number of a patent application publication must include an associated year.

Here are a few examples of common kind codes:

Kind Code Kind of document
A Utility Patent Grant issued prior to January 2, 2001.
A1 Utility Patent Application published on or after January 2, 2001
A2 Second or subsequent publication of a Utility Patent Application
B1 Utility Patent Grant (no pre-grant publication) issued on or after January 2, 2001
B2 Utility Patent Grant (with pre-grant publication) issued on or after January 2, 2001
E Reissue patent
P Plant Patent Grant issued prior to January 2, 2001
S Design Patent

Some kind codes were removed and others added during implementation of the America Invents Act (AIA). The kind codes added are:

Kind Code Kind of document
Fn Supplemental Examination Certificate published after September 16, 2012
Jn Post Grant Review Certificate published after September 16, 2012
Kn Inter Partes Review Certificate published after September 16, 2012
On Derivation Certificate published after March 16, 2013

Note that “n” in the above kind codes represents a value 1 through 9 denoting the publication sequence.

Kind codes used for patent documents published outside the U.S. vary by country. Check the kind code for the country whose patent you are examining, to ensure you have the correct type of document and stage of the publication. The WIPO Handbook on Industrial Property Information and Documentation provides a list of examples and kinds of patent documents for a number of countries.