Paper grade pulp production across the globe is dominated by the kraft process using different lig-nocellulosic raw materials. Delignification is achieved around 90% using different chemical treatments. A bottleneck for complete delignification is the presence of residual covalent bonds that prevail between lignin and carbohydrate even after severe chemical pulping and oxygen delignification steps. Different covalent bonds are present in native wood that sustain drastic pulping conditions. In this study, 100% birch wood was used for producing paper grade pulp, and the lignin carbohydrate bonds were analyzed at different stages of the kraft cook. The lignin carbohydrate bonds that were responsible for residual lignin retention in unbleached pulp were compared and analyzed with the original lignin-carbohydrate complex (LCC) bonds in native birch wood. It was shown that lignin remaining after pulping and oxygen delignification was mainly bound to xylan, whereas the lignin bound to glucomannan was for the most part degraded. Application: One central problem for the pulp and paper industry is efficiency in delignification during the chemical pulping and bleaching processes. It has been believed that one limiting factor is the covalent bonds between lignin and polysaccharides. We present data on presence of such LCC bonds in paper grade birch pulp and its development during the processes. Hopefully, this research data will be useful for the development of more effi-cient processes.