Tax calculcutation on Investment Certificate gain

Hi

I'm configuring the product  "Investmet Certificate". I entered a "100 -Investment certificates - purchase" transaction and a "200- Investment certificates - Sale" transaction, with different price.

When I did the second, it generates a derivated transaction "DBT-B001 - Security Price Gain".

I have the customer request to generate a tax over the amont of the security Price gain.

I've tried many ways, but without sucess!!

I've already configured:

1. Generate Taxes flag on product:

--> IMG --> TRM --> Transaction Manager --> Securities -->Master Data--> Product Types --> Define Company Code-Dependant Settings for the Product Type.

2. Define Tax Rates:

--> IMG --> TRM --> Transaction Manager --> Securities --> Position Management --> Securities Accoung Management --> Define Tax Rates

Here I created a record from the Update Type DBT_B001 to Update Type SE3005

Thank you