Hi there, andy.
May I know if your old account is QuickBooks Online (QBO) ? Because in QBO, it's really necessary to have a saved product when creating an invoice item to record sales transaction. It's not possible to free-write an item without saving it.
For more information about setting up a new product or service item, check out this link: Add product and service items to QuickBooks Online.
Additionally, I'll add this article to help you personalise your invoices: Customise invoices, estimates, and sales receipts in QuickBooks Online.
Comment below if you need further assistance managing your invoice items. I'm here to assist. Take care!
