On the default invoices in ArchiOffice/EngineerOffice, the title has changed from INVOICE to MONTHLY INVOICE. What if you bill more or less often than monthly?
There is a setting in ArchiOffice wherein you can configure the invoice label as per your preference. Go to Preferences-Billing-Labels and under Category: Invoice Header, change the invoice label to ‘INVOICE’ instead of the default ‘MONTHLY INVOICE'.