35 U.S.C. 251 prescribes the effect of reissue on the patent term by stating that "the Director shall… reissue the patent… for the unexpired term of the original patent."

The maximum term of the original patent is fixed at the time the patent is granted, subject to any adjustments to the number of days of extension or adjustment. See MPEP § 2720 and § 2734. While the term may be subsequently shortened, e.g., through the filing of a terminal disclaimer, it cannot be extended through the filing of a reissue. Accordingly, a deletion in a reissue application of an earlier-obtained benefit claim under 35 U.S.C. 120 will not operate to lengthen the term of the patent to be reissued.

When a reissue application has been filed in an attempt to delete an earlier-obtained benefit claim under 35 U.S.C. 120, it should be treated as follows:

1. (A) More than one "error" (as defined by 35 U.S.C. 251 ) is described in a reissue declaration, and one of the errors identified is the failure to delete a 35 U.S.C. 120 benefit claim in the original patent, or the erroneous making of a claim for 35 U.S.C. 120 benefit.

   If one of the errors identified is the presence of the claim for 35 U.S.C. 120 benefit in the patent, and patentee (1) states a belief that this error renders the original patent wholly or partly inoperative or invalid, and (2) is seeking to eliminate this error via the reissue proceeding, the Office will permit deletion of the benefit claim in the continuity data and will not object to or reject the reissue declaration on these grounds. For applications filed on or after September 16, 2012, applicant may do so by including an application data sheet that does not list the benefit claim with the filing of the reissue application or by filing a corrected application data sheet in compliance with 37 CFR 1.76(c) that deletes the reference to the prior-filed application in a pending reissue application. For applications filed prior to September 16, 2012, applicant may do so by amending the specification (if the benefit claim is in the specification) or by submitting a supplemental application data sheet in compliance with pre-AIA 37 CFR 1.76(c) (no supplemental declaration is necessary) to delete any references to prior applications. See MPEP § 601.05(b), subsection II, for more information on supplemental application data sheets. If the benefit claim is in the specification, the specification should be amended to reflect the correction even if a supplemental or corrected application data sheet is filed. Assuming the reissue declaration appropriately identifies or describes at least one other error being corrected, the reissue declaration would not be objected to for failure to comply with the requirements of 37 CFR 1.175.

   Where the reissue declaration states that the patentee is making this correction in order to extend the term of the original patent, the examiner’s Office action will merely refer to the statement in the declaration and then point out with respect to such statement that 35 U.S.C. 251 only permits reissue "... for the unexpired part of the term of the original patent."

2. (B) Only one "error" (as defined by 35 U.S.C. 251 ) is described in a reissue declaration, and that error is the failure to delete a 35 U.S.C. 120 benefit claim in the original patent, or the erroneous making of a 35 U.S.C. 120 benefit claim:
   1. (1) If the only error identified in the reissue declaration is stated to be the correction or adjustment of the patent term by deleting the 35 U.S.C. 120 benefit claim, a rejection under 35 U.S.C. 251 should be made, based on the lack of an appropriate error for reissue and failure to comply with 37 CFR 1.175.
   2. (2) If the only error identified in the reissue declaration is the need to delete a 35 U.S.C. 120 benefit claim, which the patentee seeks to now delete in the reissue application, (and no reference is made as to increasing the term of the patent), the examiner should not make a rejection under 35 U.S.C. 251 based on lack of an appropriate error for reissue and failure to comply with 37 CFR 1.175. The examiner should examine the reissue application in accordance with 37 CFR 1.176 (MPEP § 1440). A statement should, however, be made in an Office action pointing out the lack of effect (of the change in the patent) on the patent term because 35 U.S.C. 251 only permits reissue "... for the unexpired part of the term of the original patent."