The effect of additives (Al, B, N, O) on stacking fault (SF) dynamics in 3C, 2H, 4H, and 6H silicon carbide (SiC) polytypes under external loading is investigated using a combination of an axial next-nearest-neighbor Ising model and single-point energy calculations within the scheme of density-functional theory. Both hydrostatic pressure and pure shear stress are considered. Additives are considered as point defects substituting for either Si or C atoms in the SiC structure. The results of the simulations imply that the (3111) SF in 6H SiC has the highest energy of all possible stacking faults among the SiC polytypes considered. To various degrees, aluminum, nitrogen, and oxygen are found to facilitate SF induced plasticity in SiC The role of additives in promoting plastic deformation in SiC in a wider pressure range is discussed.