If you need to edit an invoice even after it has been issued, it is possible to make additional changes using the "EDIT" button in Invoice detail or in the Action menu in the list of Outgoing invoices.
In the 1st step of invoicing, you can edit:
billing address or add a new one
contact person
owner
team
In the 2nd step of invoicing, you can:
change the currency or exchange rate
re-select the budget items
add prepayment
In the 3rd step of invoicing:
change the dates
change the invoice number
add the Purchase order number
change the currency
attach proforma invoice
change notes or text on the invoice
Just to remind you, if you reselected the budget items in the 2nd step, it is necessary to use 'Generate from budget items' button.