In Spain (and others in Europe) is required to inform the "Invoice number" and "Invoice date" manually once the invoice journals are created, because this info needs to be sent to the tax authorities. Right now the invoice number is completed automatically with the voucher number, and the document date is completed with the "today date". The journals are not editable to keep the consistency between the data with the leasing module but to have these two fields editable is a must for Spain. Another field is the "Item sales tax group" but this can be solved if you inform the value directly in the main account.

The idea is to leave the invoice journal editable for the user to edit the required fileds.