How does the examiner determine if there is a serious search burden in combination-subcombination cases?

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.

In combination-subcombination cases, the examiner must demonstrate a serious search burden to justify a restriction requirement. According to MPEP 806.05(a):

“To support a requirement for restriction between combination and subcombination inventions, both two-way distinctness and reasons for insisting on restriction are necessary, i.e., there would be a serious search burden if restriction were not required as evidenced by separate classification, status, or field of search.”

The examiner determines a serious search burden by considering:

• Separate classification: The combination and subcombination are classified in different areas.
• Different status: They may have different statuses in the art (e.g., one might be an emerging technology while the other is well-established).
• Distinct field of search: Searching for one invention doesn’t necessarily cover the other, requiring additional search strategies or queries.

For example, a search for a specific type of engine (subcombination) might involve different classifications and search strategies than a search for a vehicle (combination) incorporating that engine.