How to date a patent number

Updated April 17, 2017

There are two dates associated with a patent. The first is the application filing date, which is the date on which the United States Patent & Trademark Office receives a completed patent application. The application filing date is important because it is the date from which a patent's validity is calculated. For example, most plant patents are valid for 20 years from the application filing date. The second date is the issue date, which is the date that the patent is granted. This date is important because it is the date from which the patent grantee may enforce the validity of the patent.

Retrieve the six-digit patent number. If it has any commas, omit them. For example, change 123,456 to 123456. If the patent number has less than six digits, recheck the number. If it still has less than six digits, add zeros in front of the existing digits. For example, change 1234 to 001234.

Access the internet. Go to the Patent Office's home page at Click the "Search" link under the "Patents" column on the left-hand side of the screen. Click the "Patent Number Search" link under the "PATFT: Issued Patents" column on the left-hand side of the screen.

In the query box, enter the patent number. For example, if your patent number of interest is 5146634, then enter it. Click "Enter."

The website provides information pertinent to the patent number. For 5146634, retrieve the application filing date, which is provided under the "Abstract" section on the left-hand side (September 11, 1991).

Retrieve the patent issue date, which is provided near the top of the page on the right-hand side directly under the patent number. You now have both the application filing date and the issue date of the patent number.


If you need any help with the Patent Office websites, you may call (800) 786-9199 or (571) 272-1000, or e-mail the Patent Office at

Things You'll Need

  • Patent number
  • Internet access
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About the Author

Byron Berger is a licensed attorney and registered civil engineer. Since 1998, he has contributed articles to legal and engineering periodicals, including "ADC Comment" and "Philosophical Magazine." Berger holds a B.S. in materials engineering from Michigan Technological University, as well as a J.D. from the University of the Pacific, McGeorge School of Law.