Ferinaz,
Thanks for the question. I suggest you speak with your deployment team about "self reported" tax relative to streamlining AP processes. My experience is that "self reported" tax doesn't always help. It can simplify the upfront process but then you can end up with limited accurate data to calculate the tax properly in a "self reported" process. The research we are doing at Ariba to try and address topics such as taxable, non-taxable and self-reported tax are looking into establishing integrated tax software provided by third party providers to help in real-time. As Bert mentions in his post, the actual data used to determine tax will be one of the tricky parts, such as picking vendor and picking the correct commodity. Also, taxable and non-taxable flags will be needed to address both indirect goods that are taxable, indirect goods that are non-taxable and direct materials that end up cost of goods sold and typically are not taxable. Complicated, but we are looking into the potential to help. It's taking time given the complexity.
I also suggest you consider hiring a tax consultant from a firm that knows about Ariba technology such as KPMG, Deloitte, Accenture, E&Y or others. As always with tax it's best to make sure a tax expert is involved, as you know. If you would like I can refer you to a tax providing partner of Ariba. Let me know what country and state your are in so the advisor is best positioned to give you advice.
Regards,
Joe