从保护消费者权益的角度来看，发票可以证明销售者曾提供商品或服务者发生过买卖合同或服务合同，可以保证自身的合法权益，如商品保修期的权益，防止假冒伪劣商品的侵害等。我们稍为留意一下社会生活就可理解这里面的道理。试想，我们是否发现身边经常有人因发现买回来的商品 From the perspective of the protection of consumers’ rights and interests, the invoice can prove that the seller has provided the goods or service providers have been the sale or purchase contract or service contract, you can guarantee their legitimate rights and interests, such as the rights and interests of the goods during the warranty period to prevent the infringement of counterfeit and shoddy goods . We pay more attention to social life to understand this truth. Imagine if we found someone who often found someone buying something back