Is it necessary to entrust an agency to apply for a patent?

Units or individuals applying for patents and handling other patent affairs in China may entrust a patent agency to handle them, or the applicant himself may handle them. According to the relevant provisions on entrusting a patent agency in the Patent Examination Guide, foreigners, foreign enterprises or other foreign organizations with no habitual residence or business office in China and legal persons from Hong Kong, Macao and Taiwan regions who apply for patents and handle other patent affairs in Chinese mainland shall entrust a patent agency designated by China National Intellectual Property Administration; Individuals from Hong Kong, Macao and Taiwan may entrust a patent agency or a general agency designated by China National Intellectual Property Administration to handle it;