The correct modeling of $e^+e^-$ collision events at the International Linear Collider (ILC), as well as the response of a collider detector like the Silicon Detector (SiD), is crucial to evaluating the expected sensitivity to key properties of the Higgs boson. In this document we describe the event generation and detector simulation in use for the SiD Letters of Interest submitted for the 2021 Snowmass community planning exercise.