We predict the x dependencies of deep levels produced by vacancy-impurity complexes in GaAs1-xPx. These predictions, along with those obtained earlier for the x dependencies of deep levels due to impurities, show that the slope of a deep level with x depends strongly on the site of the impurity atom for both complexes and isolated impurities. Furthermore, we find that the slopes of some of the levels produced by the vacancy complexes are very different than those associated with the corresponding point defects. We thus suggest that the theory can be used to obtain site information about the defect producing an observed level and, in favorable cases, to distinguish between levels produced by isolated impurities and those produced by complexes. We also present photoluminescence data on two unknown centers in GaAs 1-xPx and compare some of our theoretical slopes with those of the levels extracted from the data. The results show that the theory can be useful as an aid to defect identification in GaAs1-xPx x.