Withdrawal

The process of actively informing the patent office that you no longer wish to proceed with a patent application. 

It is not necessary to actively withdraw a patent application you are no longer interested in pursuing - the patent office will eventually deem it to be withdrawn when a deadline for taking action is missed.  In some cases this passive approach to abandoning a patent application may be preferable as it maintains flexibility to change your mind up until the point it is deemed to be withdrawn for missing a deadline. 

By contrast, actively withdrawing a patent application has near immediate effect and is irrevocable.  Nonetheless, there are occasions where actively withdrawing a patent application is beneficial.  For example, by actively withdrawing a patent application before the patent office has completed their preparations to publish a patent application, the publication of the patent application can be prevented - this may be desirable, for example, when faced with an unfavourable search report.  Similarly, in some situations, partial or full refunds of official fees may be available if a patent application is withdrawn at a particular time.