As a patent attorney, I’ve learned that a common point of confusion for inventors and businesses is the various numbers

associated with a U.S. patent application. If you’ve ever wondered why your patent paperwork has multiple identifiers, you’re not alone. I often get asked to clarify what these numbers mean and how they differ. In this guide, I’ll break down the most common types of numbers associated with a U.S. patent application, as follows:

• Client-Matter Number

• Application Serial Number

• Publication Number

• Patent Number

Let’s take a closer look at each, so you can better understand what they represent and how to distinguish them.

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1. Client-Matter Number

Law firms will normally assign an internal reference number to a patent project at the very beginning of the project.  The format of these reference numbers will vary from firm to firm.  At The Emanuelson Firm, each matter number includes a four-digit client number followed by a four-digit matter number and suffix, as follows:

• XXXX-YYYYZZ

The first four digits identify the client, and the second four digits identify the specific matter for that client, in sequence.  The first digit of the matter specific number identifies the type of matter, as follows:

• 1YYY: a patent matter
• 2YYY: a copyright matter
• 3YYY: a trademark matter

For utility matters, the suffix identifies the nation or region and type for the matter.  The vast majority of our Firm’s filings are in the United States, so this code will most often be:

• “US” for U.S. non-provisional utility applications
• “PR” for U.S. provisional applications
• “D” for U.S. design patent applications

Thus, the first patent matter opened for client number 1234 would be assigned client-matter number 1234-1001, and a utility patent application filed in the United States for that matter would be assigned client-matter number 1234-1001US.  If one or more continuation applications are filed on that case, an additional digit is added, starting with “1” and proceeding in sequence.  Thus, a first continuation application from 1234-1001US would be assigned client-matter number 1234-1001US1.

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2. Application Serial Number

At the time of filing of an application, the U.S. Patent and Trademark Office assigns every patent application an Application Serial Number. A Patent Attorney will typically track this number from the filing date forward. The Application Serial Number is an eight-digit number typically formatted as:

• XX/YYY,YYY

• XX/YYYYYY

• XXYYYYYY

The first two digits identify the type of application, while the last six digits are a sequential number within that series. Despite variations in punctuation or formatting, the following examples all refer to the same Application Serial Number:

• 12/345,678

• 12/345678

• 12345678

If you are unsure whether an eight-digit number associated with a patent application is an Application Serial Number or a Patent Number, a Patent Attorney can help verify it, especially when the format lacks punctuation.

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3. Publication Number

Once the USPTO publishes a patent application, it is assigned a Publication Number. This typically appears in the upper-right corner of the published application. A Patent Attorney can help interpret this number, which is often formatted with:

• A “US” prefix

• The year of publication

• A serial number

• An optional kind code (e.g., A1)

Some common variations in format include:

• US20210000001A1

• US21/000001 A1

• US 2021/0000001 A1

The third example above is generally considered the “standard” or most recognizable format. It’s important to understand this number for referencing your published application in legal or technical contexts.

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4. Patent Number

The Patent Number is assigned when a patent is officially granted by the government. After issuance, a patent will have all four numbers associated with it: the Client-Matter Number, the Application Serial Number, the Publication Number, and the Patent Number.

A Patent Number may (or may not) include:

• 6 to 8 digits

• A “US” prefix

• Leading zeroes

• Commas or spaces

• A kind code (e.g., B2)

Examples of different ways the same patent number may appear include:

• 1,234,567

• US 1,234,567 B2

• 01234567

• US01234567

The hodge-podge of formats can be confusing to clients, and sometimes even to a Patent Attorney.  The good news is that the mysteries can be solved with a bit of investigation.  The patent itself will clearly list all prior application numbers and the publication number on the front page of the issued patent, making it easier to trace the full application history and sort out the numbers.

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Why Understanding Patent Numbers Matters

Whether you’re preparing to file a patent or reviewing a granted one, knowing what these numbers represent can prevent confusion and help you communicate more effectively with your Patent Attorney, the USPTO, and potential investors or licensees. Each number plays a role in tracking your application through the patent system—from filing to publication to issuance.

If you’re unsure about any part of your patent documentation, a qualified Patent Attorney can help decode the information and ensure you’re taking the right steps to protect your intellectual property.

For assistance navigating patent numbers and the USPTO, contact Registered Patent Attorney Ken Emanuelson today: Intellectual Property Law – Contact Dallas Based Emanuelson Firm

For more information on patent basics, visit: Patent Basics | USPTO