In case changes in approval process occur (for example new phases are added, phases are deleted or the name of a phase is changed), we recommend to create a new approval process, where all the invoices pending approval will be transferred.
Please keep in mind that the old approval process should not be deleted, since it is not possible to edit, for example add an attachment to invoices returned from the archive if the previous approval process has been deleted.
First, create a new approval process with a new name in Settings - Approval process view. In case you want to include invoices pending approval to the new approval process, should those invoices first be transferred to first phase of the current approval process (Phase field on the invoice). After this, you can change a new approval process for the invoices from the drop-down menu of the field. After changing the approval process, change right phases for the invoices pending approval and save the information by clicking Save.