The paper is the result of collaborative work at NPL, K U Leuven (Belgium), University of Ferrara (Italy) and University of Bristol. The paper abstract: The Nonlinear Vector Network Analyzer (NVNA) is the workhorse for nonlinear measurements. Also, during the development of new communications systems, such as 5G, dedicated test equipment is not available. Sampling and real-time oscilloscopes offer a lower cost alternative to the NVNA but require error corrections to improve their accuracy. NPL, NIST and other NMIs have advanced this area and we summarize these corrections and their limitations, with examples, and set out guidance rules to maximize the accuracy of the results. More details are available to MORSE stakeholders and collaborators on the website.