Reduction in deep level defects and increase of carrier lifetime in 4H-SiC epilayer was observed after carbon ion implantation into the shallow surface layer of 250 nm and subsequent annealing above 1400 °C. The concentration of Z1/2 and EH6/7 traps was determined by deep level transient spectroscopy 4 μm below the implanted layer. After annealing, concentration of both traps decreased from 1013 cm-3 range to below the detection limit. Minority carrier lifetime almost doubled in the implanted samples compared to the unimplanted samples. We suggest that carbon interstitials from the implanted layer in-diffuse into the layer underneath during annealing and annihilate with carbon vacancies. Our results indicate that Z1/2 and EH6/7 traps are most likely carbon vacancy related.