a system for storing an additive solution for a vehicle engine , said system comprising a tank for storing said additive solution , a pumping module for pumping said additive solution in the tank and an electrical heating device for heating the additive solution inside the tank when freezing conditions are detected , said electrical heating device being associated with electrical connecting lines for electrical supply of the heating device , wherein the heating device comprises at least an heating module provided in a blind pocket integral with the lower wall of the tank , said pocket opening outside the tank and projecting inside the internal volume of the tank from the lower wall and said electrical connecting lines for electrical supplying of the heating device being fully provided on the outside of the tank .