How does the International Searching Authority assess unity of invention?

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 International Searching Authority (ISA) assesses unity of invention by examining whether the claims in an international application are linked by a common inventive concept. According to MPEP 1850:

“Unity of invention has to be considered in the first place only in relation to the independent claims in an international application and not the dependent claims.”

The ISA follows these steps:

• Identify the independent claims
• Determine the special technical features of each independent claim
• Assess whether there is a technical relationship among the inventions involving one or more of the same or corresponding special technical features
• If unity is lacking, the ISA may invite the applicant to pay additional fees for searching additional inventions

If the applicant disagrees with the ISA’s assessment, they can pay the additional fees under protest and request a review of the unity of invention determination.