How to manage Italian Taxes?

How to manage Italian Taxes?

I tried to setup invoices with italian taxes with no luky.
Here my request:

Article sub-total T1 = 1000
Tax1 = T1 * 4% = 40
Tax2 = (T1 + TAX1) * 20% = 208

Subtotal T2 = T1 + Tax1 + Tax2 = 1268

Tax3 = T1 * 20% = 200

Total = T2 - Tax3 = 1068

I know that I can manage Tax2 with stacked tax and Tax3 with negative number, but I can't manage this sequence.
Anyone can help me?