1, the specific treatment of the installation fee: the installation fee can be a separate line, as part of the sales details. For example, the sale of goods is air-conditioning, installation costs can be a separate line on the invoice, indicating "air-conditioning installation costs" and the corresponding amount. If the installation fee is part of a sales discount, such as buy one get one free or buy an air conditioner and get free installation, it should be clearly stated on the invoice.
2, invoicing information: in the invoice, to provide detailed information about the goods (such as name, quantity, unit price, tax rate, etc.), and based on the information to calculate the total price of the goods. Installation fees should also provide appropriate details, such as the name of the installation service, quantity, unit price, tax rate, etc., and calculate its total price.