Searching for an answer to same requirement. Has anybody found a solution? This original post is from 2007; so, I am hopeful there is some guidance.
We are on CRM 7.0, with an external tax software package.
We have a new business requirement where the 'normal' tax determination for a specific customer and product needs to be overridden to be tax exempt on specific service contract line items if our customer provided an exemption for just that line item. We could do this in the external tax package; but, we would prefer to let the person creating the contract update directly on each contract as needed.