What Are Patent Kind Codes?

Patent kind codes let you figure out what type of patent document you're looking at. The patent kind codes are on the patent, either in PDF or in print, on the right of the patent number. Patent codes are a letter, sometimes followed by a number.

What Is a Patent?

A patent is a way to protect your intellectual property or invention. When you have a patent, you're the only one allowed to sell, make, use, or import your invention. Your patent is only valid in the country where you got it. The usual term for a patent is 20 years from when you file the application. However, your patent can be deemed invalid because of court cases or other issues.

To read a U.S. patent number, you'll need to understand three parts:

  • First, the country code, which is two characters. For the United States, it is US.
  • Second, the patent/publication number. Patent applications will include the publication year before the application number.
  • Third, The WIPO Standard St. 16 kind code. The U.S. has used these since January 2, 2001.

An example patent might look like this: US 1,234,567 B1. An application might look like this: US 2017/1234567 A1.

The USPTO has two helpful resources on patent kind codes:

For more global information, the World Intellectual Patent Organization (WIPO) has the Handbook on Industrial Property Information and Documentation.

Patent Kind Codes You Should Know

When looking at patent documents, you'll see a 1968 system from West Germany that shows you the status of an application.

  • A — unexamined.
  • B — examined.
  • C — granted.

When searching databases for patents, you don't have to include this A, B, or C to find the patent you want. If you see a number after the letter, such as A1, B2, or C3, it means that part has been published that many times. Many applications become issue patents before publishing the examination. That means people typically skip B2 and go straight to C2 instead of C3, since it's only been published twice at that point.

The Derwent World Patents Index only used the letters. When the numbers were added, nobody went back to fix the already-published patents.

In the U.S., before January 2, 2001, the USPTO only did one document, which meant just the one suffix. Sometimes attorneys who deal with many patent applications create their own suffixes. This is to make the process easier for everyone to understand. It is especially helpful if submitting applications in many countries.

Example of how Kind Codes Work

When a WIPO examiner gets a patent, he or she starts with a prior art search. The applicant gets the results of the search. The search report also gets published. If it's ready when the application is published, then it goes with the application. Otherwise it becomes a separate document.

Let's say the first page, the claims, or something in the body gets published again because there were corrections. The kind codes A1, A2, and A3 would get specifications after them. However, WIPO's PCT Gazette considers any A3 document as a republication. So to search A3, look for republications in the results list.

Finally, if you're not sure which version of an application is the right one, look for the words CORRECTED VERSION on the first page. The first page also contains instructions about where the corrections are. Patent WO 2001/073119 is a good example to look at.

U.S. Patent Kind Codes

The meanings for U.S. patent kind codes changed on January 2, 2001. The codes will be different, depending on when the patent you look at was published.

The Letters Commonly Found in U.S. Codes:

  • A indicates a patent.
  • B indicates a re-examined patent.
  • E shows a reissued patent.
  • P shows a plant patent.

If you see a W followed by a number on a European patent, that means errors have been corrected throughout the document. You might find a W on multiple pages of a patent.

U.S. Codes:

  • P1 through P3 — plant patents
  • P4 and P — published plant patent applications
  • A2 — a utility patent that's been republished
  • A9 — a correction on a patent application
  • S, S1 — design
  • E, E1 — reissue
  • F1 — a corrected reissue
  • H, H1 — statutory invention registrations (SIR)
  • I4 — a defensive publication
  • I5 — an I5 trial voluntary program
  • I1, I2, and I3 — extra improvements that are outside the WF data range
  • A1 — extra improvements with codes you can find in USPTO data
  • X — a patent document that wasn't published
  • XB — a re-examination certificate that wasn't published
  • XH — the SIR was not published
  • XT — a defensive publication was not published

Kind Codes before January 2, 2001:

  • A — a utility patent grant
  • B1 through B9 — re-examination certificates

Kind Codes on or after January 2, 2001:

  • A1 — a utility patent application that's been published.
  • B1 — a utility patent grant that hasn't been published yet.
  • B2 — a utility patent grant that has been published before.
  • B8 — the correct front page of a patent.
  • B9 — a reprint of a patent.
  • C1 through C9 — re-examination certificates.
  • P2 — a plant patent grant that hasn't been published.
  • P3 — a plant patent grant that has been published.
  • P4 — the republishing of a plant patent application.
  • P9 — a correction to a plant patent application.

Codes After the American Invents Act:

  • F1 through F9 — a supplemental examination certificate from after September 16, 2012.
  • J1 through J9 — a post-grant review certificate from after September 16, 2012.
  • K1 through K9 — an inter partes review certificate from after September 16, 2012.
  • O1 through O9 — a derivation certificate from after March 16, 2013

Pre-2001 Republication Kind Codes

  • A1L — a republished A1 application, with modified claims.
  • A1M — a republished A1 application, with a different first page.
  • A2L — a republished A2 application, with modified claims.
  • A2M — a republished A2 application, with a different first page.
  • A3M — a republished A3 search report, with a different front page.

Post-2001 Republication Kind Codes

  • R1 — claims that have been amended.
  • R2 — extra search report.
  • R3 — a revised search report.
  • R4 — a search report that was published late.
  • R6 — a correction (such as corrected drawings).
  • R9 — a revised, translated search report.

European Patent Kind Codes

WIPO has created the patent kinds for European and PCT international patents. EPO applications are published 18 months after they've been filed, or 18 months after a priority date.

With European patent codes, you get either EP-A, EP-B, or WO-A documents.


  • A1 — A European patent application that's published with a search report.
  • A2 — A European patent application that's published without a search report.
  • A3 — Separate publishing of the European search report.
  • A4 — A supplementary European search report.
  • A8 — Correcting the title page on one of the A documents, such as A1 or A2.
  • A9 — Reprinting an A document, such as A1 or A2.


  • B1 — A specification on a European patent that's been granted.
  • B2 — An amendment to a European patent specification after it's gone through an opposition procedure.
  • B3 — A patent specification after there's been a limitation procedure.
  • B8 — A corrected title page for a B document, such as B1 or B2.
  • B9 — The reprint of a B document, such as B1 or B2.


  • A1 — An international application, which is published with the international search report.
  • A2 — An international application that does not have the international search report. From January 1, 2009, A2 also includes international applications that have Article 17(2)(a) declarations.
  • A3 — A publication of an international search report with a front page revision.
  • A4 — After January 1, 2009, later publishing amended claims or an amended statement, as in Article 19.

Country Codes

  • Australia — AT
  • Chile — CL
  • China — CN
  • Denmark — DK
  • Finland — FI
  • Germany — DE
  • Japan — JP
  • Korea — KR
  • Norway — NO
  • Poland — PL
  • Romania — RO
  • Serbia/Montenegro — YU
  • Spain — ES
  • Sweden — SE
  • Taiwan — TW
  • The Netherlands — NL
  • Turkey — TR

Reading European Patent Numbers

The USPTO uses 11 numbers for applications and only seven numbers for granted patents. Other countries, such as the UK, just use the same number for applications and granted patents. That means when U.S. people look at patents from other countries, they might accidentally view the wrong patents because of numerical confusion.

Instead of using different numbers for applications and patents, other countries use a suffix letter to show whether it's an application or an issued patent, such as A for application and B for granted patents. If a U.S. person finds a European patent, he or she might look at the A version when the B version is what he or she wants to look at. If you're using a patent database, you have to select the B version. Google Patents is good at showing you the B version.

What to Know About PCT Applications

PCT applications are patent applications you file under the Patent Cooperation Treaty. These international applications can be hard to understand. In many cases, you'll find that people search specific countries for applications and don't look at PCT possibilities. You might also hear them called WO documents.

Thomson Innovation reported in 2013 they had more than 2.9 million WO documents in their system. Taking into account A1, A2, and A3 codes, about 1.7 million of those are A1 applications. Of those documents, more than 500,000 have the U.S. listed as a priority country.

In 1999, the U.S. made the American Inventor's Protection Act (AIPA) a law. Looking at WO patent data, between 2001 and 2007, many patent documents were A2 documents instead of A1 documents. That shows a trend in how people were filing patents globally and in the U.S. Due to an 18-month time frame outlined in the AIPA, people had time between filing A2 and A3, instead of filing everything at once in A1.

In 2012, WO applications see more KR and CN priority country codes and fewer U.S. priority country codes. However, the U.S. still dominates. Even if U.S. priority codes are falling, companies who don't look at PCTs when analyzing patent data are making a mistake. They're missing important information by ignoring these patents.

Analyzing Patent Databases

The reason patent kind codes are important is because of databases. You need this information if you want to do patent searches or analyze patent data. In addition to kind codes, you'll come across other kinds of data in the patent searches. All seven and examples of each include:

  • Dates — the publication date, application date, and priority date.
  • Numbers — the publication number, the application number, the priority number, the citations, and family members.
  • Names assignees (which are also known as applicants) and inventors.
  • Classification codes — the kind codes from the International Patent Classification and the Cooperative Patent Classification.
  • Text Fields — titles, abstracts, descriptions, claims, and sequence data.
  • Images — diagrams.
  • Additional Information — public registry, legal status, or other.


A patent application might have three dates on it:

  • Priority Date — the date when the U.S. application was first filed
  • International Filing Date
  • International Publication Date

The publication date is going to be the easiest date to find in databases. The priority date is also important because it gives you a starting point for investment and economic research into that patent or invention. It also is when the terms of the patent start, once the application is granted, under the Paris Convention.


The International Patent Classification information will tell you what subject matter the patent deals with. Application numbers and publication numbers are important for your patent searches.

Pay attention to priority filings. These are parent patents. Additional patents for the same invention will be filed in this patent family. When you search for a patent family, the parent is usually at the bottom of the list.


A patent document will tell you the names of the people who filed the application. It might be one inventor or several.


In the patent's description, you'll find information about its history. You might discover other patent filings or information about prior art. It might tell you if the scientific research that inspired the patent had government funding.

An important part of patent text is claims. The claims section tells you what the inventor actually says is a new invention. These include apparatuses, compositions of matter, methods, processes, parameters or results you want to achieve, designs, plant claims, biotech, use, software, or omnibuses. You'll usually only find a few types of claims, and they'll be in a kind of tree.


These are diagrams, usually, that help you understand the claims text.

Extra Information

This might have to do with the cited information in a patent application. You might also get information such as legal status codes. People usually find additional patent information in regional or national patent registers. You might have to search a few databases to find all the information you want.

Frequently Asked Questions

  • How Do I File a Patent?

UpCounsel has several resources on filing patents:

How to File a Patent

How to File a Patent Application

How to Apply for a Patent

  • What Are the Best Patent Databases to Search for Patents?


Google Patents

USPTO database

WIPO database

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