What is the “relevant date” for determining prior art in PCT applications?

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.

The “relevant date” for determining prior art in PCT applications is defined in MPEP 1878.01(a), which cites PCT Rule 64.1(b). The relevant date is generally:

• The international filing date of the application
• The filing date of an earlier application if priority is validly claimed and the international filing date is within the priority period
• The filing date of an earlier application if priority is claimed, the international filing date is within two months after the priority period expired, and the Authority considers the priority claim valid

The examiner must consider the validity of the priority claim when determining the relevant date, especially when potentially relevant documents are published between the claimed priority date and the international filing date.