Non-billable Sales Order Items

Hi,

We have a requirement to sell some products and services at zero value to our customers on Sales Orders.

We want to record the sale for volume analysis purposes but we don't want to produce a Customer Invoice that shows no value.

What's best practice here? Is there a way of completing the Sales Order without producing a Customer Invoice.

I notice there is a non-billable flag on Service Order items but there is no equivalent on Sales Orders.

Lee