Key Takeaways

  • A patent number is a unique identifier that provides access to detailed information about a patent, including inventor, assignee, claims, and drawings.
  • Patent number formats vary by jurisdiction (e.g., U.S., Europe, Japan) and may include prefixes, year indicators, and kind codes.
  • Knowing a patent number allows researchers, businesses, and attorneys to verify ownership, track legal status, and assess the scope of protection.
  • Patent numbers are critical in enforcement, licensing, due diligence, and product clearance searches.
  • You can search patent numbers through official databases like the USPTO, WIPO PatentScope, EPO Espacenet, or commercial tools.
  • Specialized searches, such as a patent number search, differ from broader keyword or subject searches by targeting a single known patent.
  • Understanding how to read patent numbers (and kind codes) helps identify whether a document is a grant, application, or reissue.
  • International searches often require knowledge of different numbering systems, but INID codes provide consistency across jurisdictions.

What Is a Patent Number?

A patent number is an identifier assigned by a patent office and is used often in a patent search. The format depends on the issuing office, the type of patent, and when the patent was issued.

Patent numbers may contain a combination of several pieces of information:

  • The year the patent was issued
  • The number of the patent
  • One or more kind codes, which provide more information about the patent

For example:

  • In the United States, issued patents generally begin with "US." That is followed by the one-to-seven-digit patent number. The last part is a kind code. Each part is separated by a hyphen.
  • A U.S. Design patent number starts with a "D" or the letters "Des."
  • Some U.S. patent applications are published. A published patent application receives a publication number. This begins with U.S. That is followed by the publish year and patent number. The kind code is the last part.

Other patent offices include the:

  • European Patent Office (EPO)
  • Japan Patent Office (JPO)
  • World Intellectual Property Organization (WO or WIPO)
  • Australian Patent Office (APO)

Each patent office uses a different patent number format. Some patent offices reset the numbering each year while others don't. However, the use of year, patent number, and kind code is common.

Over time, a patent office may change the format of its patent number. That means you may notice a different patent number format depending on when a given patent was issued.

You can usually find relevant patent numbers on a commercial product or in the documentation that comes with it. Patent application or publication numbers are hard to find and may require some research.

Patent Number Formats Around the World

Patent numbers follow different formats depending on the issuing office and time of issuance. In the United States, utility patents are typically designated with the prefix “US” followed by a one- to seven-digit number and a kind code (e.g., US 7,654,321 B1). Design patents use a “D” prefix (e.g., US D789,012 S). Reissue patents include “RE,” while plant patents use “PP.” Other jurisdictions have their own systems—for instance:

  • European Patent Office (EPO): Numbers may include country codes (e.g., EP 1234567 B1).
  • Japan (JPO): Japanese patent numbers start with “JP,” often followed by year-based codes.
  • World Intellectual Property Organization (WIPO): International Patent Applications under the Patent Cooperation Treaty (PCT) use “WO” followed by the year and serial number (e.g., WO 2020/123456).
  • Australia (APO): Uses “AU” followed by numeric sequences.

Understanding these formats is essential when conducting international research, since the same invention may appear under multiple patent numbers across jurisdictions.

Why Is a Patent Number Important?

A patent number indicates that a product or invention is protected by a patent. That means the patent holder can stop other people from using patented property. He or she can also sell or license the patent.

Patent numbers are also valuable to anyone doing patent research. With a patent number, you can look up the details of the patent.

Practical Uses of a Patent Number

Patent numbers are more than just identifiers; they play a role in many practical scenarios, including:

  • Product Clearance: Businesses can confirm if a product is protected before launching competing goods.
  • Licensing and Sale: Investors and companies use patent numbers to verify ownership before negotiating a licensing deal or acquisition.
  • Enforcement: Patent owners use numbers when sending cease-and-desist letters or filing infringement lawsuits.
  • Due Diligence: Patent numbers help attorneys and investors assess the strength of intellectual property portfolios.
  • Research and Innovation: Scientists and engineers review patents by number to learn from prior art and avoid duplication.

By tying an invention to a patent number, companies and individuals reduce risk and gain legal certainty in commercializing products.

What Information Can I Find With a Patent Number?

Once you have found the patent associated with the patent number, you can see all the information in the patent. This includes:

  • Inventor's name
  • Patent holder's name
  • Patent issue date
  • Patent title
  • Type of patent
    • Utility, Design, or Plant Patent
    • Patent Application Publication: Published patent application
    • Reissued Patent: Reissued with changes to a previous patent
    • Defensive Publication or Statutory Invention Registration: Documents that argue against issuing a patent
  • Current class number (CCL)
  • Term extension notice (if applicable)
  • Application number, date, and other related patents or applications
  • U.S. and international classification information
  • Cited references
  • Primary and assistant examiner names
  • Name of attorney or firm
  • Abstract summary
  • Drawings and/or designs
  • Specifications and claims

Patent formats vary by country. However, countries share common labeling using INID codes. That means even if you don't read the language, you can tell what field you're looking at.

How to Read Patent Numbers and Kind Codes

Every patent number includes elements that tell you what type of document you’re looking at:

  • Kind Code: Indicates whether the document is an application, granted patent, or corrected/reissued document. For example, “A1” often designates a published application, while “B1” designates a granted patent.
  • Prefix Codes: Letters like “D,” “RE,” “PP,” or “H” in U.S. patents signal design, reissue, plant, or statutory invention registration, respectively.
  • Publication Year: In international filings, the year of publication is often part of the number (e.g., WO 2021/123456 A1).

Learning how to interpret these codes ensures that you know whether a patent is still pending, has been granted, or has undergone changes.

How Do I Search for a Patent Number?

There are several ways to find a patent number.

PatFT contains full text records for patents issued from 1976 to now. It also contains images of older patents. However, you need to know the patent number or classification to search for them.

  1. To search this database, enter whatever information you have about the patent. This can include:

    • Patent holder's name

    • Inventor's name(s)

    • Keywords related to the invention

    • One Boolean operator, like AND, OR, or ANDNOT

  2. Define your search by selecting the kind of information you have entered.

  3. Select the year range you want to search.

  4. Click "Search."

  • PatFT Advanced Search

  1. Go to the same page as PatFT Quick Search. Choose "Advanced" at the top of the page. Advanced search allows you to use command line syntax. Keep in mind:

    • Advanced search terms are not case-sensitive. However, Boolean operators must be capitalized.

    • Certain words, like "various" and "invention" are excluded as search terms because they are too common.

    • Use the field codes listed below the search box to define your search.

    • Searches have a 256-character limit. To find the character length of your search, right-click on the results hit list and choose "Properties."

  2. Narrow the year range of your search. Otherwise, it will default to the full database.

  3. Click "Search."

Patent Number Search vs. General Patent Search

A patent number search is different from a traditional patent search. Instead of scanning for all documents related to an inventor, company, or technology area, this search is limited to one known patent. It is a faster, more precise method because the number acts as a direct key to the record.

By contrast, a general patent search may require using keywords, classification codes, or inventor names to find a range of results. Businesses often begin with a patent number search when investigating a specific product, then expand into broader searches for prior art or related patents.

How Do I Search for a Patent Using a Patent Number?

Once you know the patent number, go to a patent database:

From there, you can enter the patent number to find either the abstract or the full patent record.

Get familiar with the USPTO website. Here you can find drawings and full texts of patents that were once only available in Washington D.C. and certain large libraries. From the homepage:

  1. Click "Patents."
  2. Click "eSearch Patents" under "Services."
  3. Click "Patent Number Search."
  4. Enter the patent number, including "D" if you're looking for a design patent. Do not include commas.
  5. Click the blue patent number in the lower left corner.
  6. Click "Images."

You can also search for international patents. First, decide which country's patents you want to search. Then figure out how that country formats its patent numbers. (For example, Japanese patent numbers start with "JP.")Search international patents with a global patent search tool:

International Patent Number Searching

International patent research requires familiarity with different numbering systems and search platforms. Some of the most widely used resources include:

  • WIPO PatentScope: Searches PCT applications and international publications.
  • EPO Espacenet: Offers access to over 140 million worldwide patent documents.
  • National Patent Offices: Each jurisdiction (e.g., Japan, Canada, Australia) maintains its own searchable database.

Despite differences in format, most patent documents use standardized INID codes, which allow researchers to identify bibliographic data such as inventor, assignee, and filing date regardless of language.

Frequently Asked Questions

1. Where can I find a patent number on a product?

Patent numbers are often printed directly on the product, packaging, or in accompanying documentation. Some companies use “virtual marking” by listing patents on their website.

2. What does the kind code at the end of a patent number mean?

A kind code indicates the document type, such as a published application (A1) or a granted patent (B1). Different countries use different systems, but INID codes provide consistency.

3. Can I search for an international patent number in the USPTO database?

No. The USPTO database only covers U.S. patents. For international searches, use WIPO PatentScope, EPO Espacenet, or the respective national patent office database.

4. What’s the difference between a patent application number and a patent number?

A patent application number identifies the filing before it is granted, while a patent number is assigned after the patent has been issued.

5. Do expired patents still have active numbers?

Yes. Patent numbers remain permanent identifiers, even after a patent expires. However, expired patents no longer provide exclusive rights.

If you need help with a patent number, you can post your question or concern on UpCounsel's marketplace. UpCounsel accepts only the top 5 percent of lawyers to its site. Lawyers on UpCounsel come from law schools such as Harvard Law and Yale Law and average 14 years of legal experience, including work with or on behalf of companies like Google, Menlo Ventures, and Airbnb.