An invoice starts as a draft: change anything, delete it, no number yet. When you finalise it (or download or send a draft), Blanqo:
- gives it the next number of your range, without gaps and never twice,
- locks its content – as German law (GoBD) and most tax authorities require,
- stores the PDF with a fingerprint (SHA-256), so you can always prove what was sent,
- records it in the invoice’s history: finalised, downloaded, sent, status changes.
After that only the status changes (sent, paid, overdue, cancelled). To correct a mistake, create a credit note and, if needed, a new invoice. A finalised invoice cannot be deleted.