Certified Reference Materials (CRMs) are essential for high-quality measurements. However, CRMs are sometimes unavailable. In such cases, the comparability of measurements can be maintained to some extent if homogeneous and stable reference materials (RMs) are available. In this chapter, we present examples of the preparation and use of RMs for total dissolved inorganic carbon (DIC) and total alkalinity (TA) in seawater. One example is a working RM produced in-house by JAMSTEC, whose use has been limited to R/V Mirai cruises. The other is the KANSO TECHNOS CO., LTD (KANSO) RM, which is commercially available in Japan. Both RMs have been used to check the performance of instruments for DIC and TA analyses and to maintain the comparability of the measurements together with the globally used RM from Scripps Institution of Oceanography. We also discuss issues related to maintaining RM production and the possibility of wider distribution of RMs.