A decision last year of the Federal Court of Appeal stated a clear rule about the relationship between the patent office and patent agents: once a patent issues, most aspects of the patent application process are beyond challenge (Weatherford Canada Ltd. v. Corlac Inc., 2011 FCA 228):
 To be clear, the concept of abandonment in paragraph 73(1)(a) operates during the prosecution of the application for a patent. Its operation is extinguished once the patent issues.
As a result of the decision, parties challenging the validity of an issued Canadian patent may no longer point to a lack of good faith when responding during the prosecution process as a basis of invalidity.
While this decision applies to patents that have issued, the patent application process contains many potential pitfalls for an unwary, careless or unlucky patent applicant that may not be covered by this decision, some of which are highlighted below.
The patent office will only recognize correspondence from the ‘authorized correspondent’ which is typically the patent agent appointed by the patent applicant. Problems can arise if someone other than the authorized correspondent attempts to pay a fee or respond to the patent office. This may occur if the applicant has recently changed patent agents or if the applicant corresponds directly with the patent office.
In a number of cases, for example in Excelsior Medical Corporation v. Canada (Attorney General), 2011 FCA 303 and Rendina v. Canada (Attorney General), 2007 FC 914, the courts have refused to recognize annual fees paid by someone other than the authorized correspondent while the application is pending resulting in the loss of the patent rights in Canada.
Once a patent issues, the situation is different and anyone can pay annual maintenance fees.
The patent office often issues ‘office actions’ to the applicant requisitioning the applicant to respond or correct certain defects in the patent application.
Section 73(1) of the Patent Act states that an application is “deemed to be abandoned” if the applicant does not reply in good faith to any requisition.
The courts have held that an office action response timely filed by the applicant that fails to address every requisition results in the abandonment of the application, without necessarily any notice to the applicant.
 Thus, where an applicant fails to respond to a requisition and the application is not reinstated within the year provided to rectify the situation, the patent application is abandoned as a matter of law. There is no discretionary decision which is reviewable by the Court.
There are at least half a dozen different sections of the Patent Act and Patent Rules that allow the patent office to requisition information or fees from the applicant. It may not always be clear if a document issued by the patent office is making a single requisition or multiple requisitions. In fact, the patent office itself recently clarified its own position on the issue of multiple requisitions in 2003.
Inadvertently missing a requisition when filing a response to an office action can result in the deemed abandonment of the patent application which, if not rectified, results in the irrevocable loss of the patent application possibly without further notice to the applicant.
Notices of Abandonment
While the patent office typically issues a Notice of Abandonment to the authorized correspondent if a deadline was not met, or fees were not properly paid, such notices are not mandatory and sometimes are not delivered to the authorized correspondent.
Usually, the applicant has sufficient time after receiving a Notice of Abandonment to rectify the situation. In Canada, an applicant has one year from the date of the abandonment to reinstate the patent application. If the Notice of Abandonment is not received or not handled quickly enough, the one year period may expire and the application may die.
In Eiba v. Canada (Attorney General), 2004 FC 250, Justice Mosley held that there is no requirement in the Patent Act or Patent Rules that the patent office notify applicants of any deficiencies, and furthermore that applicants cannot rely on the notices that are typically provided:
[The applicant] chose to rely on the Commissioner's informal practise of notifying agents that applications were not in good standing prior to the expiry of that period. As I have concluded above, the Commissioner was under no duty to provide such notice. In the circumstances, I can find no remedy for the applicant.
The Patent Act, Patent Rules and patent office practices are complicated and full of potential “catastrophic consequences”, as the Federal Court of Appeal has written, consequences that are often disproportionate to an inadvertent oversight or error. While the resulting patent may have great value to an inventor or applicant, and be immune to many challenges to its validity, there unfortunately remain many occasions to lose the patent application along the way.