We have implemented and evaluated a software platform for 4D online dose reconstruction. We have shown that dose can be calculated and accumulated in real-time at 25 Hz for the whole lung volume using a clinical voxel resolution utilizing precalculated dose-influenced **data** and DVFs. We could demonstrate for a limited patient cohort how decreased PTV margins lead to inadequate target coverage during untracked delivery for patients with substantial motion. Moreover, we observed that MLC centroid tracking successfully recovers the GTV target dose for these patients. OAR doses were consistently reduced by reducing PTV margins. 