CAFC Rules in Chitlik v. HHS: 'Reasonable Diligence' Does Not Require Maximum Feasible Effort in Mailing

WISECODE Take

The U.S. Court of Appeals for the Federal Circuit, in its August 10, 2026 decision (Case No. 2025-1804), clarified the boundaries of "reasonable diligence" in procedural delays. The author notes that many business owners mistakenly believe that any late filing automatically forfeits their rights, or that they must use the most extreme delivery methods to fulfill their legal duties. The petitioner, Laurence Chitlik, mailed his application 10 days before the deadline for an 85-mile journey, yet it arrived one day late due to USPS delay. The court ruled that reasonable diligence does not mean maximum feasible diligence; petitioners are not required to constantly monitor tracking or resend documents at their own expense upon realizing a delay. While this reduces the risk of trademark loss due to third-party postal errors, it does not protect those who habitually file on the very last day. Zhidian offers patent portfolio health check services to help businesses systematically review the safety margins of their filing timelines. First, businesses should aim to mail international patent filings at least 10 days before the deadline. Second, always retain original mailing receipts and postmarks to serve as evidence for restoring rights in the event of systemic delays. Proactive timeline planning remains the best strategy against external uncertainties.