A tight‐binding treatment of (100) heterojunctions with common anions is performed. A new zero‐dipole approximation is presented together with a first‐order correction that explicitly depends upon the static macroscopic dielectric constant. The difference between the zero‐charge and zero‐dipole approximations is discussed. These two approximations are then compared to a complete self‐consistent calculation and shown to provide band offsets within 0.1 eV of the exact value. The corrected zero‐dipole treatment gives a much better accuracy of order of 0.02 eV. Agreement with experiment is very good for the three lattice matched systems: AlAs–GaAs, CdTe–HgTe, and AlSb–GaSb.