When a patent application is published, interim rights start to accrue, which allow the patent applicant to sue for infringement damages, if and when the patent is ultimately granted depending on the relationship between the claims in the application and the finally granted claims. Interim rights may be enforced if a party performs actions that would infringe the invention claimed in a published patent application, that party has actual notice of the application, and the claims in the issued patent are substantially identical to those in the published application. An infringement action must also be initiated within six years of the patent being issued.
However, warning letters with respect to claims of interim rights are unwise because they may induce a potential infringer to oppose the grant of the patent in the relevant patent office. Interim rights are also referred to as “provisional rights.”