Often, a different tax is applied for different types of products, e.g. 0% tax for membership fee, 20% tax for products like t-shirts, 5% tax for books,... With invoice manager, tax can only be applied to the subtotal. I would like to have option to select tax for each product, so I can put items with different tax groups to the same invoice. Also, what I'm missing is an option to enter the discount in percent, and let the invoice manager calculate the discount value.