External system invoice number pass to SAP

Hi,

I have a requirement to pass the external billing system invoice number and also the same number into FI document for further usage for payment clearing SAP. The external system invoice number will be passed on in a flat file via interface which we use to create first the sales order using BAPI and further on billing using the standard job using the sales order (This is order related billing). We will agree with the external system to give us the external number range which we will define in the SAP system and make the number range to be external (or) we use a z-table to take the number range object to create the billing document in the specific number range within that range.

1) My question how do we force the system to use the external number (probably we will keep the external system invoice number in some field like PO number while creating the sales order) to use while creating the billing. Does the system always take sequential number from the external number range and create the invoice (or) can we force the number in some billing user exit to have overwritten with the number I want taken from sales order PO field ? Can we have technical details how to achieve this please ?

2) Once I achieve the question 1 then I can use the order to billing copy control to populate the current billing document as assignment or reference number via config, I guess ?

3) Another question related to the process - we will be disabling the MWST tax calculation in SAP and take the tax amount from the external system to directly pass in the pricing...currently we have existing process to populate the prices...which tax condition type will be suitable for passing the external system tax amount ...is it MWEX (External VAT) ? If it so, how do we associate with a tax code for the tax amount passed externally ? do we have pass the tax code as well ?

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Cheers

Murali

Message was edited by: Jyoti Prakash