Rule 109 Statement [Patent] Law and Legal Definition

Rule 109 statement is a statement made by a patent examiner giving the reasons for allowing a patent claim. Whenever the record does not adequately reflect the reason for allowing a patent claim, an examiner can file a Rule 109 statement. Rule 109 statement should include at least: (1) the major difference in the claims not found in the prior art of record, and (2) the reasons why that difference is considered to define patentability over the prior art if either of these reasons for allowance is not clear in the record.

A Rule 109 statement does not purport to contain a complete (or standing alone, comprehensible) rationale as to why a patent has been allowed. Its function is essentially supplementary, to fill in gaps or holes in the file record by which a reader might be confused as to one or more reasons for allowance of one or more particular claims. [Leeds v. Commissioner of Patents & Trademarks, 955 F.2d 757 (D.C. Cir. 1992)]