) to reduce the cost of higher-level calculations, such as CCSD or CCSD(T). This simple yet effective idea has been pioneered by Bartlett and co-workers in the context of the ground-state CC calculations. The benchmarks have shown that significant computational gains can be achieved while introducing insignificant errors in the relative energies, barrier heights, and optimized geometries . However, calculations of response properties have proven to be more challenging, requiring modification of the approach .