In the practice of substantive examination for inventions in chemistry or medicine, the technical effects often depend on experimental data. However, in many cases, it is difficult for the applicant to search for all the prior art before filing the application and the comparison documents cited in the examination stage. If the experimental data was insufficiently recorded in the original specification, it is likely to be questioned by the Examiner. Therefore, to prove the inventive steps of the invention patent application, the applicant may need to submit supplementary experimental data to prove it.
However, CNIPA (China National Intellectual Property Administration) is stringent  on acceptance and consideration of supplementary experimental data submitted by applicants. 
The following will discuss the practice of submitting supplementary experimental data in China.
I. Legal grounds 
For the examination of supplementary experimental data, the related provisions are as follows: 
i) Section II, Chapter X of Guidelines for Patent Examination states: “With respect to experimental data submitted after filing date, the Examiner shall make an examination. The technical effects to be proved by the supplementary experimental data shall be obtained by a person skilled in the art from the disclosure of the application document.” (Revised Guidelines for Patent Examination (effective on April 1, 2017)) 
ii)Article 11 of Regulations on certain issues concerning hearing administrative cases of patent authorization and right verification (draft , issued by the Supreme People’s Court on April 29, 2020 for public opinions.) states: “When the patent applicant or the patentee of a medicine invention submits experimental data after the filing date to further prove that the technical effects provided in the description are sufficiently disclosed, and the technical effects could be determined be a person skilled in the art from the description, drawings and common knowledge in the art on the filing date, a people’s court generally shall make an examination.
When the patent applicant or the patentee of a medicine invention submits experimental data after the filing date to prove that the patent application or patent has different technical effects with those of Reference, and the technical effects could be obtained directly and undoubtedly from the disclosure of application document by a person skilled in the art on the filing date, a people’s court generally shall make an examination.”
It can be seen that the provision to accept supplementary experimental data by the court also is that the technical effect can be obtained directly and undoubtedly from the disclosure of the application document.
II. Requirements for supplementing experimental data 
Whether the supplementary experimental data can be accepted depends on whether the technical effect proved by the experimental information can be “obtained” from the content disclosed in the patent application. Whether it can be "obtained" depends mainly on whether the experimental data is recorded in the specification, if the experimental data is not recorded in the specification, or if the experimental data does not prove that the effect can be achieved, it is considered the effect cannot be obtained from the specification, and even if the applicant/patentee submits supplementary experimental data, it cannot be used to prove the effect.
When submitting supplementary experimental data, attention should be paid to the timing, data format and data content of the submission.
(i) Submission timing
You can submit experimental data in the stages of substantive examination, reexamination, invalidation, or legal proceedings. But whether the data can be finally accepted will have different considerations in different stages. 
In the substantive examination or reexamination stages, the experimental data is relatively easy to be accepted. This is mainly reflected in the two following aspects: Low requirements for the formality of evidence—for example, evidence formed abroad does not require notarization and legalization, and does not require a translation by designated translation agency; No third party questioning procedure—the Examiner can decide whether to accept the data through his judgment. 
Once further proceedings are involved, such as invalidation and subsequent administritive litigation, it becomes more complicated. In addition to the higher requirements for the formality of evidence, there are often disputes over the authenticity and relevance of the experimental data. The third party often disregard it. In this case, if there is no other supporting evidence, the supplementary experimental data will be more challenging to be accepted.
(ii) The formality of supplementary data
There is no uniform requirement for the formality of experimental data. Usually, the applicant needs to compare the technical effect of the present invention with the closest comparison documents cited by the examiner to compare the effect data. Such comparison data is the most intuitive.
If the data is formed outside of China, at the stage of invalidation or administrative litigation, the data needs to be notarized by the notary office of the host country and certified by the embassy of the People’s Republic of China in that country. 
If the data is in a foreign language, it usually needs to be translated into Chinese.
(iii) Contents of the experimental data
a. The technical effect of the experiment data needs to be clearly recorded in the original application document; otherwise, it is very likely that the evidence will not be considered;
b. Generally, comparison data between the present application and the closest prior art should be provided;
c. The experimental data should correspond to the scope of the claims.
III. Practical advice 
For patent applicants and patentees, when the patentability of their inventions is questioned, submitting additional experimental data is a possible way that could be taken. In addition, when drafting an application document in chemical/medicine field, conservatively, the experimental data should be recorded in the specification, for meeting the requirement of sufficient disclosure or for verifying the unexpected technical effects. 
The patent applicant should try to submit relevant evidence during the examination and reexamination process before the patent grant when it is needed to provide additional examples and experimental data to prove the inventive step of the invention. 
In the follow-up legal litigation process, although there is the possibility of submitting new evidence, the difficulty of accepting the supplementary experimental data will be increased. If the applicant needs to provide supplementary experimental data to prove the inventive steps of the invention, it is recommended to submit it during the examination or reexamination process before the patent is granted. 

References:
1. Analysis of Train of thoughts of Supplementary Experimental Data Review. CNIPA Reexamination Department, LIU, Tingting.
http://reexam.cnipa.gov.cn/alzx/scjdpx/fswxjdpx/21948.htm
2. Consideration of supplementary experimental data in creative judgment. CNIPA. Reexamination and Invalidation Department，CHEN, Yanyan, WU Tong yi.
http://reexam.cnipa.gov.cn/alzx/scjdpx/fswxjdpx/22145.htm