Note! On the invoices marked as received or partially received you can only modify the data that does not affect the final sum.
To modify an outstanding invoice click on the invoice number on the invoice list.
You can also find the Modify button in the invoice detailed view.
In the modify view, you can see the Delete button only if you have the relevant rights to delete sales documents. The right to modify and delete invoices is regulated with permission sets under Settings > Administration > Permission sets.
If you've enabled an accounting and finance integration to sync invoices from Scoro, for example, the Xero integration, then all modifications and deletions will be synced to the other software.