How to create rates for invoices in QBO

I am trying to add an invoice line item that is a % of the subtotal on the invoice.  I can add the subtotal line but can't create a product/service that is actually a % (rate) vs. flat fee.  I type 3% into the field and it converts it to .03 flat rate - not a %.  It then shows up as .03 in both the rate and amount columns of the invoice...not a % calculation.  I'm using QBO by the way and all online reference seems to be about the desktop version.