The Quick Add button appears on the message QuickBooks displays when you
enter a name, item, class, account, customer type, vendor type, payment method,
payment terms, or shipping method that QuickBooks has no record of.
Clicking Quick Add creates a new list entry based on what you enter into the
form you are working with. For example, if you enter a new customer name on an
invoice, clicking Quick Add adds the new customer to the Customers & Jobs list and
adds to the customer's record all information you enter about the customer
on the invoice form (billing address, payment terms, taxable status, etc.).