This Practice Note deals with the various ways that a patent owner can amend its patent.

There are several different ways to amend a patent, at various stages of its life, and depending on whether the application for the patent originated in the UK Intellectual Property Office (UK IPO), the European patent Office (EPO) or under the international Patent Co-operation Treaty (PCT) system.

Patent amendment is not freely allowable because this would mean the goalposts shifting on where the boundaries of the patent owner’s monopoly rights lie. This is not acceptable in a patent system where the owner has exclusive or so-called ‘monopoly’ rights, since the public accessing the register of those rights must be able to determine whether or not they might infringe the patent, without the patent changing its scope over time.

On the other hand, it is not possible to definitively know at the time of applying for a patent, the existence of every possible piece of Prior art, for example. So if prior art comes to light later, it should be possible to amend the patent