COPA document in ETO (Engineer to Order) Scenario with milestone billing

Hi All

I have some issue in COPA document generation in ETO Scenario.

In ETO scenario, we have following important points

--- Milestone billing (30 % downpayment, 60% on shipping and remaining 10% with closing invoice) in the Billing plan.

--- We have dropship ment kind of scenario where the Purchase requisition is created while creation of Sales order.

--- While GR for PO whill be statistical and we will be booking COGS in GR

We have an issue in COPA document while billing. The quantity field is not getting updated.

Please help.

Regards

Neeraj Bhardwaj