This section is structured as follows: initially, the Q-CC3 results are presented and a comprehensive analysis is conducted to benchmark the impact of the basis set on 𝛿 TPA . Subsequently, the accuracy of the lower-order methods is assessed across the entire set of states. This assessment encompasses evolution of the method performance across diverse 𝛿 TPA ranges, considering the molecular dimensions, and the nature of the states, namely valence, Rydberg, and states showing a significant double excitation character.