The Daniel K. Inouye Solar Telescope (DKIST), formerly Advanced Technology Solar Telescope when it begins operation in 2019 will be by a significant margin Earth's largest solar research telescope. Science priorities dictate an initial suite of instruments that includes four spectro-polarimeters. Accurate polarization calibration of the individual instruments and of the telescope optics shared by those instruments is of critical importance. The telescope and instruments have been examined end-to-end for sources of polarization calibration error, allowable contributions from each of the sources quantified, and techniques identified for calibrating each of the contributors. Efficient use of telescope observing time leads to a requirement of sharing polarization calibrations of common path telescope components among the spectro-polarimeters and for those calibrations to be repeated only as often as dictated by degradation of optical coatings and instrument reconfigurations. As a consequence the polarization calibration of the DKIST is a facility function that requires facility wide techniques.
