The tax bureau knows whether there is an official seal through the lower right corner of the invoice. Through the lower right corner of the invoice, you can see whether the official seal is used. If the official seal is stamped on the lower right corner, it proves that the official seal is used, and vice versa. The official seal refers to the seal used by organs, organizations, enterprises and institutions. Because the Ministry of Public Security has not made uniform provisions on the engraving procedure, the provisions on the engraving procedure vary from place to place. According to the different types of seals, the procedures are different.