Experimental studies on the speciation of berkelium in carbonate media have shown that complexation of berkelium(III) by carbonate results in spontaneous oxidation to berkelium(IV) and that multiple species can be present in solution. We studied two proposed structures present in solution based on theoretical comparisons with spectroscopic data previously reported for Bk(IV) carbonate solutions. The multiconfigurational character of the ground and low-lying excited states in both complexes is demonstrated to result from the strong spin-orbit coupling. Although bonding in berkelium(IV) carbonate and carbonate-hydroxide complexes is dominated by strong Coulombic forces, the presence of the non-negligible covalent character is supported by ligand-field theory, natural localized orbitals and topological studies of the electron density. Bond orders based in natural localized molecular orbitals (NLMOs) show that Bk–OH bonds possess enhanced orbital overlap that is reflected in the bond strength.