This Microsoft Excel document contains 5 worksheets providing data produced by research as part of UKCCSRC Call 1 funded project (grant number UKCCSRC-C1-31) and UKCCSRC funded international exchange. These data are presented and discussed in the manuscript "Geochemical tracers for monitoring offshore CO2 stores" by J. Roberts, S. Gilfillan, L. Stalker, M. Naylor, https://doi.org/10.1016/j.ijggc.2017.07.021. Then data details the assumptions around background concentrations of chemical tracers in the atmosphere and seawater, cost per litre, and how tracer detection concentrations (and so cost and potential environmental impact were calculated).