Self Assessment EB Tax - Apply tax on Percentage of Line amount

Hi All
I have a client requirement (US client) on self assessment in Oracle EBusiness tax
Can anyone help to suggest the solution.

Business wanted to do self assessement on particular vendor. This scenario is specific to one vendor.

They want the tax rate to apply on 9% of the Line amount ( Basically taxable amount = 9% of Invoice Line amount)

They will self assess this amount and pay to the government. Currently they are doing out of EBS.

I need help on the above scenario how to set up in EB tax to automatically calculate the self assessed tax on the invoice wb from this specific vendor.