Damage waiver or, as it is often referred to, collision damage waiver (CDW) or loss damage waiver (LDW), is optional damage insurance coverage that is. What is Supplemental Liability Insurance (SLI)?. Norway car rental insurance question ~ Trying to decline CDW. Hi Bees, I would like to update DH's auto insurance policy since we have started riding together to work, and I feel that his current coverage.