The United States Pharmacopeia–National Formulary and its Supplements become official six months after being released to the public. The USP–NF, which is released on November 1 of each year, becomes official on May 1 of the following year.
This change was adopted to give users more time to bring their methods and procedures into compliance with new and revised USP–NF requirements.
The table below describes the new official dates. The 2008 USP31–NF26, and the Supplements and Interim Revision Announcements (IRAs) to that edition, will be official until May 1,
2009, at which time the USP32–NF27 becomes official