How can Canon guarantee 20 17 without an invoice?

If the invoice is not issued, the seller can make up the invoice (or receipt) with the shopping receipt. If the seller refuses to issue an invoice, he can also enjoy the warranty with the serial number of the fuselage. Different manufacturers will start the warranty from the factory date 1-3 months. Specifically, you can go to the after-sales maintenance point for consultation or call the official customer service phone to consult the warranty situation.