Tax calculation

Hi

We are implementing indirect procurement in a country were the tax code calculation is a bit complicated. We want the system to calculate the tax in as many cases as possible. The problem we are having is that for a certain product category the tax can differ depending on what the expense is being used for. For this is seems the SRM setup is not enough. Does anyone have a smart solution for these more "complicated" tax calculations? Do we have to split all the product categories? We would like to avoid that since we are using UNSPCS as a template.

Any suggestions would be great!

Thanks

/Anders