The relative energies of the X˜,a˜andA˜ states of CBrCl and its atomization energy in the complete basis limit were determined by extrapolating (spin restricted) CCSD(T), MRCI and EOM-CCSD energies calculated with the aug-cc-pVxZ (x=T,Q,5) basis sets which were corrected for core-valence correlation, scalar relativistic and spin–orbit coupling effects. The geometries and vibrational frequencies were calculated at the B3LYP/cc-pVTZ density functional and CASPT2/cc-pVTZ levels of theory. The predicted heat of formation at 298K is 68.0±1.0kcalmol −1 . The calculated singlet excited state vibrational frequencies and A˜←X˜ excitation energy are in close agreement with experiment.