How to exclude discount line to be calculated tax where source is DOO and discount is separate line

Tax is being calculated on both the main item line and the discount line, resulting in double tax calculation. The customer wants tax to be calculated only based on the price list ( main item line) and not after applying the discount.

The application is calculating tax on both the item amount and the discount amount, causing reducing tax as discount line amount is negative for rate basis or duplicate tax calculation for quantity basis tax.

Bangladesh Tax authority instruction is Tax should be calculated only based on the original price list amount and should not be recalculated after applying the discount.