In Peru there is a 18% IVG tax.  I think it might be considered some form of VAT.  When we send invoices, we bill for the price of the product and nothing else.  The price includes the tax.  However, the invoice must show the total (eg. 720) and also show the IVG tax amount ($109.83) and the value sold "Valor Venta" of $610.17.  How do I get this to work correctly and show correctly on the invoice?