Which of the following is a requirement for changes to inventorship in Non-Provisional applications?

Changes to inventorship in non-provisional patent applications necessitate an inventors' oath or declaration. This requirement ensures that any individual being added as an inventor consents to the change and acknowledges their contribution to the invention. The oath or declaration serves as formal documentation that validates the inventors' intent and commitment to the information provided in the application.

In the context of patent law, the inventors' oath or declaration is critical because it reinforces the principle that an inventor must be someone who has contributed to the conception of at least one claim in the patent. This documentation acts as a safeguard, ensuring that all recognized inventors are fully aware of their involvement and responsibilities pertaining to the patent application.

The other options involve different considerations but do not fulfill the requirement for changing inventorship. For instance, a written agreement from the original inventors might clarify relationships among them but does not replace the need for a formal oath or declaration. Similarly, proof of funding or payment of additional fees relates more to financial or administrative aspects of the patenting process rather than specifically addressing the legal status of inventorship. Therefore, the requirement of an inventors' oath or declaration is pivotal in effecting any changes to inventorship in non-provisional applications.