Starting with version 8.6.0, you may now have multiple possible invoice formats so that those 'special' customers who have to have an invoice that is different from the rest can be accommodated.  As the default, there will be two invoice formats available:  the current default invoice format and a simpler one.  If you require others to be created, we can do this for you at a nominal cost depending on the complexity of the requirements.  To set the default for a customer, select the Defaults tab for your customer under Administration/Maintain Clients.  It will look something like the image below.  Just select the item in the Invoice Report dropdown and remember to save.  Once this is done, this report will be the one that is used to create the invoice for you client, to view it later, email it and any other function used to view an invoice.