Create STO Invoices Flow from STO PO

Hi,

I need to create STO invoice but I m stuck in the Shipping Doc Flow.

Here are the steps that I had completed.

1) Create STO PO.

- Purchase Doc Type: ZB

- T-COde: ME21N

2) Create Outbound Delivery for STO PO

- T-Code: VL10B

3) Create Shipment with reference to the delivery

- T-code: VT01N

- I executed the Planning, shipment start, shipment & Shipment Completion in Deadline Tab.

4) Create Shipping Cost Doc

- T-code: VI01

I put in the Shipping Number and execute.

Why the NET Value becomes 0. And because of this, I cant transfer the shipping cost calculation.

appreciate helps.

Thanks.