Documents published on dates falling between the date of filing of the application being examined and the date of priority claimed, or the earliest priority if there is more than one (see B‑VI, 5.2, and B‑XI, 4), are denoted by the letter "P". The letter "P" is also given to a document published on the very day of the earliest date of priority of the patent application under consideration. The document category "P" is always accompanied by a symbol indicating the relevance of the document according to B‑X, 9.2.1 or B-X, 9.2.2, for example: "P, X"; "P, Y"; or "P, A".[Rule 61(3); ]
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/b_x_9_2_4.htm
Date retrieved: 17 May 2021