When is a foreign patent considered available as a reference?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

Generally, a foreign patent is considered available as a reference on the date it becomes enforceable. This is typically the date when the sovereign formally bestows patent rights to the applicant. As stated in the MPEP:

“The date the patent is available as a reference is generally the date that the patent becomes enforceable. This date is the date the sovereign formally bestows patents rights to the applicant.” (MPEP 2126.01)

However, there is an exception to this rule when the patent is secret at the time the rights are awarded.