How does the USPTO determine the effective filing date for foreign priority claims?
For U.S. patent documents claiming foreign priority, the USPTO determines the effective filing date based on the description of the subject matter in the foreign application. MPEP 2154.01(b) states:
If subject matter of a U.S. patent document under examination is not described in the earliest application to which benefit or priority is claimed, the effective filing date is the earlier of: (1) the filing date of the earliest application in which the subject matter is described; or (2) the actual filing date of the patent or application under examination.
This means that for foreign priority claims, the USPTO will examine the foreign application to ensure it adequately describes the claimed subject matter. If it does, the foreign filing date becomes the effective filing date for that subject matter.
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