Polarisation degree vs. the normalised rest frame phase for SLSNe-I with polarimetric data highlighting the diverse decline rates (top) and spectroscopic phase of each epoch of polarimetry (bottom). The stretch factors used to normalise the decline rates are shown in the legend. The top axis refers to the number of magnitudes declined by the SNe based on the linear fits. Only slowly evolving SLSNe-I have shown non-zero P, but the Fast ones have not been observed sufficiently late on in their evolution to rule it out. Spectroscopically, the SLSNe-I exhibit low polarisation during the Early phase, but no relation to polarimetry can be identified at the later phases. We note that SN 2018ffj is not shown due to the unconstrained peak time and SN 2020tcw is not shown in the bottom panel due to uncertain spectroscopic phases during the polarimetric epochs.