At present, the safest approach is to rely on MBE(n) as an efficient means to apply post-HF correlated wave function methods to large systems, starting from a SIEfree HF calculation and aggressively screening the correlated calculations. In this way, second-order Møller-Plesset (MP2) calculations have been demonstrated in which a small-basis HF calculation for the entire system is used to recover long-range polarization, with short-range MBE(3) calculations to describe electron correlation, with a total cost that is dramatically reduced with respect to conventional MP2 calculations. In future work, we will extend this approach to coupledcluster calculations that can achieve benchmark accuracy for thermochemistry and non-covalent interactions.