Administrative Instructions under the Patent Cooperation Treaty

Section 109
File Reference

(a)  Where any document submitted by the applicant contains an indication of a file reference, that reference shall not exceed 25 characters in length and may be composed of either letters of the Latin alphabet, or Arabic numerals, or both. The hyphen character ("‑") may also be used as a separator between alphanumeric characters.

(b)  Correspondence from International Authorities intended for the applicant shall indicate any such file reference.