By locking an invoice, tampering can be prevented, once it has been sent out.
The addressee company, products and currency in a locked invoice cannot be changed.
Lock / unlock an individual invoice
In the invoice detail view, the options panel has a lock/unlock option, which is visible to users with permission to lock/unlock.
Lock multiple invoices
From the invoice export overview, a user can lock invoices by month.
The invoice export can be accessed via Invoice > Invoice export by users that have permission to "list export invoices".
Permission to lock/unlock
An internal user needs permission to lock/unlock. This setting can be changed in the permission panel in the internal user admin view. This is accessible via system settings > internal users > choose a user.
The user action log keeps track of changes to the invoice lock.