How can the applicant actively modify the patent application documents? Is there a time limit?

After the filing of a patent application, the applicant may propose amendments on his own initiative, but the time and scope of the amendments need to be specified. Article 5 1 Detailed Rules for the Implementation of the Patent Law:

Paragraph 1: When making a request for substantive examination, an applicant for a patent for invention may, within three months from the date of receiving the notice from the patent administration department of the State Council that the application for a patent for invention has entered the substantive examination stage, voluntarily propose amendments to the application for a patent for invention.

Paragraph 2: An applicant for a patent for utility model or design may, within two months from the date of filing, voluntarily propose amendments to the application for a patent for utility model or design.

All amendments to the application documents shall comply with the provisions of Article 33 of the Patent Law:

The applicant may modify his patent application documents, but the modification of the application documents for patents for inventions and utility models shall not exceed the scope recorded in the original specifications and claims, and the modification of the application documents for patents for designs shall not exceed the scope shown in the original pictures or photographs.