What is the difference between reexaminations ordered under 35 U.S.C. 304 and 35 U.S.C. 257?

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 MPEP distinguishes between reexaminations ordered under different statutory provisions:

1. Reexaminations ordered under 35 U.S.C. 304:

• These are standard ex parte reexaminations
• The certificate states “Reexamination Request” before the filing date and number
• They continue an established ordinal numbering sequence

2. Reexaminations ordered under 35 U.S.C. 257:

• These result from a supplemental examination proceeding
• The certificate states “Ex Parte Reexamination Ordered under 35 U.S.C. 257”
• The certificate states “Supplemental Examination Request” before the filing date and number
• They have a separate and new ordinal sequence, beginning with “(1st)”

The MPEP notes: If the reexamination proceeding was ordered under 35 U.S.C. 257 as a result of a supplemental examination proceeding, the certificate is also titled “Ex Parte Reexamination Certificate.” In addition, the certificate will state “Ex Parte Reexamination Ordered under 35 U.S.C. 257”.