This Practical Law Practice Note by Charley Macedo discusses key milestones in post-grant patentability challenges at the U.S. Patent and Trademark Office under the Leahy-Smith America Invents Act (AIA). It reviews typical timelines and procedures at key milestones in inter partes review (IPR), post-grant review (PGR) and covered business method (CBM) patentability challenges before the Patent Trial and Appeal Board (PTAB).