What is the difference between a free warranty invoice and a VAT invoice?

Warranty invoices are issued by merchants to indicate that you can go to him for free repair vouchers, although the invoice, but does not involve the amount of money, and does not involve the transaction behavior, so it can not be used for reimbursement. But the VAT invoice is the merchant precisely from the tax office to spend money to buy, you go to buy things he has to open this kind of invoice to you, this kind of invoice on the amount and tax (invisible), that you did consume, and paid the tax. So you can take it for reimbursement, get it?