Certificate of destruction
The short answer
A document from whoever destroyed the material, saying what was destroyed, how much of it, by what method and when. No law defines it, which is exactly why the detail on it matters.
In practice
It is a commercial assurance, usually for confidential paper, hard drives, backup tapes or branded stock that must not reappear. Because nothing sets its contents, a good one names the items, the weight, the method, the standard, the site and the person who signed it, and a weak one says little more than the customer's name.
Two other documents share the name and are not this. The DVLA Certificate of Destruction is issued by a vehicle treatment facility when a car is scrapped. A WEEE evidence note is the statutory record of electrical waste treated, and only an approved facility can issue one.
Where LoadSnap touches it
LoadSnap issues certificates from the receipt or collection the material arrived on, so the items and weights cannot drift from the transfer note, and each one carries a code the customer can verify.