where R is the rotation operator, M denotes spin projections in the original coordinate system, and S z is a spin projection in the rotated coordinate system. In the case of singlet-triplet SOCC, D 0 0,0 =1. One can compute matrix elements 00|H SO |10 by EOM-EE (as reference-EOM matrix elements) and EOM-SF (as EOM-EOM matrix elements) or 00|H SO |11 by EOM-SF (reference-EOM) at three different molecular orientations and solve the system of linear equations. By randomizing the signs of the SOC elements, we established that phase inconsistency affects the final result of SOCC when the latter strategy is used. The same test yields identical values of SOCCs if 00|H SO |10 is computed.