Invoice hash chain
In one sentenceLinking each e-invoice to the hash of the invoice before it, so that deleting or editing an invoice after it is issued can be detected.
Simply put
A hash is a digital fingerprint calculated from the invoice's content: any change in a single character changes the whole fingerprint.
Each invoice carries the fingerprint of the previous invoice, forming a chain from which nothing can be removed without it showing.
Example
If an invoice were deleted from the middle of the day in a point-of-sale system, the next invoice would point to a fingerprint that no longer exists, so the deletion is exposed.
Don't confuse it with
Cryptographic stampThe hash proves the integrity and order of the content, while the stamp proves the invoice was issued by your registered system.