Rapid growth of marine surface robotic systems has created the need to define principles allowing assessment of technical reliability and safety, when certification is needed to get operational permissions. IMO MASS Code is being developed to deal with autonomous ships of a certain size and purpose. Third-party surveys during design and construction are not always possible if based on the rules developed for these ships. The number of R&D projects for the construction of small unmanned surface vehicles has created demand for technical assistance and certification as requested by marine administrations and market and customer expectation. This presentation will outline the PRS experience related to the USV certification process.