What are the typical circumstances where adequate written description issues arise in patent applications?

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 MPEP 2163.03 outlines three typical circumstances where adequate written description issues arise:

• Original claims: When the claims define the invention in functional language specifying a desired result but the specification does not sufficiently describe how the function is performed or the result is achieved.
• New or amended claims: When the claims are not supported by the original specification.
• Description requirement vs. enablement: When there is a question whether the specification provides adequate written description to support the claimed invention.

The MPEP states: “The fundamental factual inquiry is whether the specification conveys with reasonable clarity to those skilled in the art that, as of the filing date sought, applicant was in possession of the invention as now claimed.”