How to add a separate tax line to the accounting order detail

[Rémi]

I have a small problem with PrestaShop (1.5.4.1) and I can not find the solution.

I am told that you are the best person to answer me.

Here are:
Customers receive by email an "order details" with a tax price line, an added tax line and it's perfect. (see color image)

On the other hand, the accounting receives an "order details" with the amounts with tax included only. (see image in gray)

How to add a separate tax line to the accounting order detail too, to be like that of the customer?

Thank you for answering me