Generally speaking, business licenses, product quality certificates or trademark registration certificates can be used as legal basis for selling goods.

1. Business license: A business license is a necessary document for a company to carry out business activities, including important information such as company name, type, business scope, registered capital, etc. When selling goods, sellers should provide a true and valid business license.

2. Product quality certificate: According to relevant laws, regulations and industry standards, some products need to undergo quality testing and certification, and obtain corresponding certificates of conformity before they can be sold on the market. If the seller can provide relevant quality certificates, it means that the quality of its products has been officially recognized.

3. Trademark registration certificate: Trademarks are an important part of product brands. When selling goods, you should use trademarks that have been registered and obtained trademark rights, otherwise it may infringe on the intellectual property rights of others. Sellers can provide their own certificate of trademark registration to prove that their goods are genuine.

Counterfeiting refers to the act of selling fake and shoddy goods or covering up or tampering with the true condition of the goods to mislead consumers. When selling goods, you need to abide by relevant laws, regulations and business ethics, provide true, accurate and complete product information, and use legal channels to purchase and sell goods.