MPEP 2163.04
Burden on the Examiner with Regard to the Written Description Requirement

Ninth Edition of the MPEP, Revision 07.2022, Last Revised in February 2023

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2163.04    Burden on the Examiner with Regard to the Written Description Requirement [R-11.2013]

The inquiry into whether the description requirement is met must be determined on a case-by-case basis and is a question of fact. In re Wertheim, 541 F.2d 257, 262, 191 USPQ 90, 96 (CCPA 1976). A description as filed is presumed to be adequate, unless or until sufficient evidence or reasoning to the contrary has been presented by the examiner to rebut the presumption. See, e.g., In re Marzocchi, 439 F.2d 220, 224, 169 USPQ 367, 370 (CCPA 1971). The examiner, therefore, must have a reasonable basis to challenge the adequacy of the written description. The examiner has the initial burden of presenting by a preponderance of evidence why a person skilled in the art would not recognize in an applicant’s disclosure a description of the invention defined by the claims. Wertheim, 541 F.2d at 263, 191 USPQ at 97.


In rejecting a claim, the examiner must set forth express findings of fact which support the lack of written description conclusion (see MPEP § 2163 for examination guidelines pertaining to the written description requirement). These findings should:

  • (A) Identify the claim limitation(s) at issue; and
  • (B) Establish a prima facie case by providing reasons why a person skilled in the art at the time the application was filed would not have recognized that the inventor was in possession of the invention as claimed in view of the disclosure of the application as filed. A general allegation of "unpredictability in the art" is not a sufficient reason to support a rejection for lack of adequate written description. A simple statement such as "Applicant has not pointed out where the new (or amended) claim is supported, nor does there appear to be a written description of the claim limitation ‘____’ in the application as filed." may be sufficient where the claim is a new or amended claim, the support for the limitation is not apparent, and applicant has not pointed out where the limitation is supported.

    See Hyatt v. Dudas, 492 F.3d 1365, 1370, 83 USPQ2d 1373, 1376 (Fed. Cir. 2007) (holding that "[MPEP] § 2163.04 [subsection] (I)(B) as written is a lawful formulation of the prima facie standard for a lack of written description rejection.").

When appropriate, suggest amendments to the claims which can be supported by the application’s written description, being mindful of the prohibition against the addition of new matter in the claims or description. See Rasmussen, 650 F.2d at 1214, 211 USPQ at 326.


Upon reply by applicant, before repeating any rejection under 35 U.S.C. 112(a) or pre-AIA 35 U.S.C. 112, para. 1, for lack of written description, review the basis for the rejection in view of the record as a whole, including amendments, arguments, and any evidence submitted by applicant. If the whole record now demonstrates that the written description requirement is satisfied, do not repeat the rejection in the next Office action. If the record still does not demonstrate that the written description is adequate to support the claim(s), repeat the rejection under 35 U.S.C. 112(a) or pre-AIA 35 U.S.C. 112, para. 1, fully respond to applicant’s rebuttal arguments, and properly treat any further showings submitted by applicant in the reply. When a rejection is maintained, any affidavits relevant to the 35 U.S.C. 112(a) or pre-AIA 35 U.S.C. 112, para. 1, written description requirement, must be thoroughly analyzed and discussed in the next Office action. See In re Alton, 76 F.3d 1168, 1176, 37 USPQ2d 1578, 1584 (Fed. Cir. 1996).