The Court of Appeals for the Federal Circuit in Transco Products v. Performance Contracting recently ruled that it is not required that the best mode of carrying out an invention be updated when a continuation application is filed. This decision reversed a controversial district court decision that held that the best mode had to be updated when a continuation application was filed.

The Federal Circuit in overruling the district court stated that the district court had "erred as a matter of law in holding that an applicant must update the best mode disclosure upon the filing of a continuation application containing no new matter." The Federal Circuit distinguished between continuation, divisional and continuation-in-part applications, stating that the best mode does not have to be updated when filing a continuation or divisional application. The Federal Circuit relied on the wording of the statutes granting priority for earlier-filed U.S. and non-U.S. patent applications and on case law which provides that continuation applications are part of the earlier-filed application as to common subject matter and compliance with the best mode requirement of U.S. patent law is based on the filing date of the original application.

The Federal Circuit also noted that the addition of an updated or new best mode would constitute new matter and thus "deprive the applicant of the benefit of the earlier filing date of the patent or original disclosure for any claim whose validity rests on the new best mode disclosure."

In addition, the Federal Circuit pointed out that much of continuation practice is due to formal requirements of the Patent and Trademark Office (e.g. restriction requirements, requiring the filing of a continuation application after final rejection to permit entry of an amendment) and to require contacting the inventor to see whether there is an updated best mode would constitute an undue burden.

The Federal Circuit did state that if there is a claim in a continuation-in-part application that is not supported by the disclosure in the parent application that claim is only entitled to the filing date of the continuation-in-part application and the disclosure in the continuation-in-part application must include the best mode for carrying out the invention defined by that claim.