“…The paper [7] established the Hyers-Ulam stability of a system of firstorder linear differential equations with constant coefficients, followed by [8,9]. Other recent papers on HUS and differential systems include [3,4]. In this work, we sharpen and clarify those results, in the 2 × 2 constant coefficient matrix case, by providing necessary and sufficient conditions for the linear system to be Hyers-Ulam stable, and we suss out specific Hyers-Ulam constants in the event of Hyers-Ulam stability, including specific cases with the minimal constant.…”