Sometimes, after filing the invention patent application, you may find some defects in your application documents, or want to amend or add some content. At this point, you may adopt the following measures to amend the invention patent application.
 
I. Initial amendments

1. Occasions for the amendment

2. Limitation on amendment
Article 33 of the Patent Law provides the limitation on the amendments: an applicant may amend his patent application documents, provided that the amendment to the invention or utility model patent application documents does not exceed the scope specified in the original written descriptions and claims.
 
II. Passive amendments

1. Occasions for the amendment
Passive amendments refer to the amendments made under a circumstance other than the above-mentioned circumstances in which the amendments are initiated by the applicant. Amendments have to be made in response to the examination opinions provided by the examiner in the office actions with a view to overcome the defects in the description, the claims, or the drawings.
2. Limitation on amendment
In responding to office actions, there are several limitations on how the patent application may be amended. 

Ⅲ. Filing divisional application

If the applicant wishes to seek protection for the contents in the initial application or the contents to which patent right is not granted in the initial application, may file a divisional application on the aforesaid contents. Contents to which patent right is not granted can be the claims pointed out by the examiner as lacking unity, or the claims not acceptable due to limitation of amendments to the office action.
By filing a divisional application, such claims can have another chance for examination.
1. Occasions for filing a divisional application
The applicant shall file the divisional application within two months from the receipt date of the Notification to grant the patent right to the initial application (i.e. the time limit for responding to the Notification and completing the formalities for granting);
For the initial application that the examiner has issued a Decision of rejection, the applicant may submit a divisional application within three months from the receipt date of the decision rejecting the initial application, regardless of whether an application of reexamination for challenging the rejection is filed; the applicant also may file a divisional application after the request for reexamination is made or during the administrative lawsuit if not satisfied with the decision of the reexamination.
2. Limitation on amendment
A divisional application should not go beyond the scope of disclosure contained in the initial application. Otherwise, it shall be rejected on the ground that it does not comply with Rule 43. 1 or Article 33.
 
Ⅳ. Re-filing of a Patent Application

The above mentioned measures, no matter initial/passive amendments or filing divisional application, are all limited to the initial filed document. If the applicant found the application documents have serious defects or the application can be optimized during the application procedure, the above mentioned measures are not applicable.
In this case, the applicant may re-file the application, claiming the priority of the initial application within 12 months from the filing date of the original application, after modification and improvement of the technical solutions.