The main objective of this article is to present our proposal of complex customer loyalty measurement within external feedback loops as a response of Industry 4.0 concept in the area of advanced quality management for business-to-business (B2B) relationships, as customer loyalty and organisational sustainability are two critical factors for long-term success. To reach the goal, deep literature analysis, special field research, interviews with specialists, and development of a new model of closed-loop quality management systems, which are created for Quality 4.0 environment, were used. A new term, complex customer loyalty, is introduced, and twelve basic steps of its measurement are briefly explained, including a set of loyalty indicators, all regarding specific characteristics of B2B context. Special research confirmed that only about 15% of Czech organisations use some systematic approach to customer loyalty measurement within B2B area. In the majority of Czech B2B organisations, closed-loop quality management systems are mostly in early phases of their development. However, there is no doubt that complex customer loyalty measurement will be an important part of these systems. The proposals presented in this article are mostly universal and should be applied not only to Czech companies.