SCAR is a document associated with a Certificate of Origin that allows artist, galleries, or collectors know the artwork associated with a specific COO may have an issue.
The SCAR allows anyone in contact with the piece to know the state of the work and helps to keep everyone ethical and honest in all dealings with the artwork.
(Example: if a gallery sells a work with a COO attached and the artist is never paid for the work, the artist can issue a SCAR on the COO until the artist is paid.)