Hi there, and thank you for your answer.

I will post today a new little version that correct some problems.

For the price excluding vat on the checkout page, the problem is that Ubercart don't provide hook to alter the subtotal, and the subtotal is calculated by adding the product price * quantity in the cart.

So, to alter the subtotal I'm obliged to alter the cart, that's why I return to excluding price in the checkout page.

As it said below (and this is the way I proceed), the best way ATM is to disable the cart block in the checkout page, and change the title to the cart pane to specify that prices are excluding VAT.

I will improve that when Ubercart will provide these functionnalities because it's a think I don't really like too.

Edit : New version updated