What is the significance of the “A” and “B” series in patent kind codes?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

The “A” and “B” series in patent kind codes generally indicate different stages of the patent process. According to MPEP 901.04(a):

• “A” series: Typically refers to patent application publications or first-level publications.
• “B” series: Usually indicates granted patents or second-level publications.

For example, in the U.S. system:

• A1 denotes a Patent Application Publication
• B1 signifies a Utility Patent
• B2 indicates a Utility Patent issued after reexamination

This system helps quickly identify whether a document is a published application or a granted patent, which is crucial for determining its legal status and potential relevance in prior art searches.