How to Setup Tax calculation on Margin Amount (Item Cost-Price)

Summary:

Hi Experts

Can you please how to setups tax, So that It can calculate Margin Amount (Item Cost-Price)

Requirement:-

Please find the formula used by CPQ for calculating the VAT for used cars. 

Item Cost = X

Price (incl Discount) = Y

Margin Amount = Z

VAT = V

Z = Y-X

V = Z * 0.15

Total Price from Customer = Y + V

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