Electronic timestamp

An electronic timestamp binds a document, or more precisely its hash, to a date and time issued by a timestamping authority. Anyone can later verify that the document has not been changed since that moment. Under eIDAS a qualified timestamp, issued by a qualified trust service provider, enjoys a presumption of accuracy of the time and of the integrity of the data.

Timestamps are used to renew the validity of signatures whose certificates expire, to prove when a document was archived, and to show that an invoice or a record was not altered after the fact. Several certified invoicing regimes, including the Spanish Verifactu rules, rely on the same principle by chaining records with hashes and time data. In digital bookkeeping a timestamp is an inexpensive way to strengthen the audit trail of archived documents.