Excise duty calculation on Assessable value in PO

Dear Team,

We are facing critical issue in Excise Duty calculation, Excise is calculating on basic price for our normal procurement and we are selling the same at MRP cost... Now the issue is Excise Duty has to be calculated on Assessable value (65% on MRP value) instead of basic price in PO.

Example:

Basic Price - 100

MRP - 300

Assessable value - 195

Excise Duty - 24.10 (195*12.36%)

Regards,

Sai