Client has design invoice how to make as default the created by client .please note they issued few invoice already

Hello Info1106, 

Welcome to the Community page, 

To clarify your client has created their own invoice template that they want to us in Quickbooks?

If this is so, in order to do this if they go to 

Cog wheel>custom form styles>click new style>import style> invocie>next> browse find the saved template> next follow the steps, this will upload the invoice template for them to then use. when there create an invoice if they click on customise bottom middle of the page then tick the correct template then go to print preview and it will show the invoice in that template form ready to send to customer.