VeriFactu
Every invoice and ticket becomes a chained VeriFactu record with its QR, sent to the AEAT.
Apps are turned on from the Apps page of your Hub. Create your free account to get one.
VeriFactu turns every document Invoicing issues into its billing record for the Spanish tax agency: chained to the previous one by its SHA-256 fingerprint, with the QR the customer can check, validated against the AEAT's official schemas and sent in order, respecting the waiting time the AEAT asks for. What cannot go out waits in the queue and leaves by itself; a rejected record is corrected with a new one. Records, queue, audit events and the chain's recovery are all here, in the test environment until you go live.
This app needs these apps, which turn on with it: