This document specifies the general principles for justifying the product claims for plant biostimulants. It is applicable to all application types of plant biostimulants. General principles consist of and define all general parameters, requirements and quality criteria, and are intended to be applied in order to assess the efficacy of trials used for claim(s) validation as a result of the use of a plant biostimulant. This document is aimed primarily at manufacturers, laboratories, researchers, technical centres, companies that will put the products on the market, notifying authorities, notified bodies, and market surveillance authorities.