Scratch Off is a process to cover printed data with a opaque covering so it cannot be read until the final user removes the coating to read the data. Most often used for gaming or lottery tickets.
This Scratch Off feature is effective primarily in document-present situations where the original document can be examined by a trained professional or scanned with a specialized 3-illumination ID scanner and analyzed with adequate forgery detection technology.
Usability in online and mobile onboarding situations is challenging as the examination is made not on the physical document but on a photograph or scanned image of it.
Ref.: https://www.perfectcloud.io/resources/glossary/