A critical evaluation and optimization of all available phase diagrams and thermodynamic data of the binary Sn–RE (RE=Gd, Tb, Dy, Ho, Er, Tm, Lu and Y) systems was conducted to obtain reliable thermodynamic functions of all the phases in the system. In particular, the thermodynamic properties of liquid phase were described using the Modified Quasichemical Model which takes into account the short range ordering of solution. The systematic analysis and the uncertainties in the Sn–RE systems were discussed.