Platinum is among the rarest elements on the planet, and the understanding of its formation and transport through aqueous fluids in the Earth, at high pressure and temperature, may help in the identification of new deposits. While complexation of platinum with sulfides, chlorides, and hydroxyl has been the topic of numerous investigations, the interaction of Pt and carbonates in aqueous fluids under pressure remains largely unexplored. Here, we present extensive first-principles molecular simulations of Pt (bi)carbonates at conditions (1 GPa, 1000 K and 11 GPa, 1000 K) relevant to the Earth crust and upper mantle and we predict how the metal speciation varies as a function of pressure and how it depends on its oxidation state. Furthermore, we compute Raman spectra and identify vibrational signatures that may be used to characterize the varied species in solutions. Our simulations provide valuable inputs to the Deep Earth Water model.