If an application is filed in the US claiming priority from a foreign application, what date determines the AIA 102(b) one-year grace period?

The correct answer is the foreign filing date, as it establishes the basis for the one-year grace period under the America Invents Act (AIA). When a patent application is filed in the United States and claims priority to a foreign application, the priority date corresponding to the foreign application becomes critical in determining the time available to file a U.S. application without concern for prior art.

Under AIA 102(b), if the foreign application was filed before the U.S. application, the filing date of the foreign application is treated as the priority date for assessing whether any disclosures made by the inventor or others during the one-year period preceding the U.S. filing date constitute prior art against the U.S. application. This grace period allows inventors to publicly disclose their invention or to take steps to commercialize it without losing patent rights, as the U.S. application is still considered actively protected under the foreign application’s filing date.

Consequently, reliance on the foreign filing date facilitates international patent strategies and encourages inventors to seek protections across multiple jurisdictions while retaining rights that might otherwise be forfeited due to public disclosures made before filing in the U.S.