Invoice refers to the business vouchers issued and collected by all units and individuals in buying and selling goods, providing or receiving services and engaging in other business activities. It is the original basis of accounting, and it is also an important basis for law enforcement inspection by audit institutions and tax authorities.

Nanjing (abbreviated as Ning), known as Jinling and Jiankang in ancient times, is the capital of Jiangsu Province, a sub-provincial city, a megacity and the core city of Nanjing metropolitan area. Nanjing Province is located in the southwest of Jiangsu Province, in the lower reaches of the Yangtze River. It starts from 3 1 14' N in the south, ends at 32 37' N in the north, ends at 1 18 22' E in the west and ends at 1 19 E in the east. Nanjing Province is the shipping and logistics center of yangtze river international, an important gateway city of the country driven by the radiation of the Yangtze River Delta, one of the four ancient capitals of China, and an important birthplace of Chinese civilization. It is known as the "ancient capital of the Six Dynasties" and "the capital of the Ten Dynasties", and has the reputation of "the literary hub in the world" and "the first study in the southeast".