The band gaps were measured via diffuse reflectance UV-Vis spectroscopy on powders of samples for the series SrxBi4-xO4Se1-xCl2+x and CaBi3O4Cl3. Figures ) and (b) show tauc plots as a function of x for the direct and indirect gap respectively. For the values of x = 0.75, x = 0.95 and x = 0.99 two onset features are observed in different energy ranges; these were extracted as EG direct, EG indirect, EG direct 2 and EG indirect 2. The observation of two transitions for x = 0.75, x = 0.95 and x = 0.99 is of particular interest due to the application of SrBi3O4Cl3, in photocatalysis. SrBi3O4Cl3, is a known photocatalyst, the introduction of ingap states with Se addition may allow for two-photon absorption processes that allow for photocatalytic activities across a broader spectrum of incident light.