Transforming the raw HUT data to flux and wavelength calibrated spectra requires several steps. Important transformations include corrections for wavelength shifts induced by image motion, pulse persistence resulting from the phosphor decay time, dark-count subtraction, dead-time corrections, scattered light subtraction, subtraction of second-order emission, flat-field corrections, and multiplication by the inverse sensitivity curve. Additional corrections to the overall flux scale to correct for light lost due to image motion are also made. To take advantage of the statistical properties of the photon-counting HUT detector, we compute and propagate an error array for each step in the data reduction process. We describe each of the corrections to the HUT data in more detail in the following sections.