By Christopher P. Singer —

The U.S. Patent and Trademark Office has posted on the top page of the EFS-Web portal site an advisory that the system will be unavailable because of system maintenance.  According to the advisory, the maintenance is scheduled to begin at midnight and end at 4 a.m. on Sunday, May 31st (EDT) — obviously a window of time with minimal filing activity.  During this period, the electronic business center states that EFS-Web will be unable to process (1) National Stage applications filed under 35 U.S.C. § 371; (2) follow-on documents to existing applications; (3) real-time online fee payments; and (4) Customer Number selection list for Registered e-Filers.