The utilization of interferometric stitching with coherence scanning interferometers has allowed these instruments to measure much larger areas than a single site measurement would permit. This has a major impact on the measurement of mid-spatials and form for freeform optics, which is hard or impossible through traditional means. The local slopes of these freeforms lead to non-null fringe measurements. These non-null measurements cause aberrations that are known as retrace errors. Minor retrace errors can influence stitching, which create form and mid-spatial errors that are orders of magnitude larger than the initial aberration. The aberrations caused by retrace errors can be calculated and corrected for. In this thesis, the stitching of a planar, mild freeform, and plano-convex optic are compared to a traditional technique: Fizeau interferometry. Retrace errors for coherence scanning interferometry based on non-null measurement is experimentally quantified. This information is then used to write a point by point correction in MATLAB based on local slope. The correction is implemented and assessed on a full stitch of a freeform optic. Finally, this thesis will explore expanding this process to other coherence scanning interferometers as well as other freeform and aspheric optics.