Why didn't the electronic invoice for patent application payment be sent to the mailbox?

Network delay. The reason why the electronic invoice was not sent to the mailbox after the patent application was paid is because of the network delay. Patent system is a legal system to protect the intellectual property rights of inventions and creations under the conditions of market economy. Patent application is a necessary procedure for obtaining patent right. To obtain a patent right, the applicant shall file an application with the State Patent Office, which shall approve and issue a certificate.