Tax calculation with early payment discount - A/P with Vertex

Looking at the BOE site for California it looks like the tax amount should be calculated based on the Voucher amount less the early payment discount (if taken) not on the original vouchered amount. The tax amount currently remains unchanged whether or not the early payment discount is taken. Some states allow this, others don't as some consider the discount taken as income to the customer. I previously worked with Vertex in SAP and these rules could be set up state by state but I'm not sure where to do this in JDE. Any help would be appreciated.

Thanks,

Carlos