Semilocal density functionals, when applied to the CO-metal system, over-stabilize the LUMO (2π*) and HOMO (5σ) of the CO molecule due to the charge delocalization error inherent in these functionals . In this context, the 5σ orbital, which contributes to bonding, favors the top site, while the 2π* orbital prefers hollow sites . This overemphasis on 2π* interactions causes semilocal density functionals to incorrectly predict hollow or bridge site preference, rather than the experimentally observed top site adsorption at low coverages . Unlike DFT-based methods, FNDMC does not suffer from any charge delocalization error . Addressing this issue in a system-independent manner is essential for accurately modeling catalytic processes involving CO*, as adsorption sites and energies directly influence reaction pathways and kinetics.