Can a supplemental examination request be filed for an expired patent?
Yes, a supplemental examination request can be filed for an expired patent. The MPEP 2816 states:
“A request for supplemental examination may be filed at any time during the period of enforceability of a patent.” This includes the period after the patent has expired.
The MPEP further clarifies: “The period of enforceability is determined by adding 6 years to the date on which the patent expires. … However, 35 U.S.C. 257(c)(2)(B) provides that the Director may not commence an ex parte reexamination of a patent under 35 U.S.C. 257 if the request for supplemental examination is filed on or after the date that is 3 months before the expiration of the term of the patent.“
This means that while you can file a request for supplemental examination after the patent has expired (within the enforceability period), the USPTO may not initiate an ex parte reexamination if the request is filed too close to or after the patent’s expiration date.
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