How to renew the patent when it is about to expire?

An annual patent fee is required for each patent year. If that's what you mean by expiration date, you can call the patent office for payment consultation and confirm the payment amount according to the patent number.

The protection period of a patent is 20 years from the date of filing, 20 years for invention, and 10 years for utility model and design. If the deadline is about to expire, there is no need to pay the fee because the deadline is fixed.