The Criminal Procedure Law stipulates that the supplementary investigation should be completed within one month. Supplementary investigation is limited to two times. After the supplementary investigation is transferred to the people's procuratorate, the people's procuratorate recalculates the time limit for examination and prosecution.

The supplementary investigations are as follows:

1. If it is found that the facts are unclear, the evidence is insufficient, or the accomplices and suspects are omitted, it is necessary to make supplementary investigations or provide supplementary evidence;

2. It is necessary to supplement or change the prosecution, although it is not necessary to supplement the investigation and provide evidence when the omission of the suspects or the omission of the criminal facts in the same case is discovered.

The number of times the procuratorate returned to the public security supplementary investigation was:

1. The return of supplementary investigation by the procuratorate refers to a litigation activity in which the people's procuratorate further investigates some facts in the case and supplements evidence on the basis of the original investigation work in accordance with legal procedures. The case is examined and prosecuted by the procuratorate, and supplementary investigation will be considered only after returning to the public security.

2. Article 140th of China's Criminal Procedure Law stipulates that when examining a case, the people's procuratorate may request the public security organ to provide evidence materials necessary for the trial.

3, the people's Procuratorate to review the case, for the need for supplementary investigation, can be returned to the public security organs for supplementary investigation, can also be their own investigation. A case under supplementary investigation shall be completed within one month. Supplementary investigation is limited to two times.

4. After the supplementary investigation is transferred to the people's procuratorate, the people's procuratorate recalculates the time limit for examination and prosecution. If the people's procuratorate still believes that the evidence is insufficient and does not meet the conditions for prosecution, it may make a decision not to prosecute.

5. There are two situations of supplementary investigation. That is, if the public security organ terminates the investigation and the people's procuratorate needs supplementary investigation after examination, it may decide to return the case to the public security organ for supplementary investigation, or it may decide to conduct investigation on its own, and ask the public security organ for assistance when necessary. However, if the people's procuratorate needs to make supplementary investigation on a case that has been investigated by itself, it cannot be returned to the public security organ for supplementary investigation.

To sum up, the supplementary investigation of a case generally needs: within one month. The Criminal Procedure Law stipulates that the supplementary investigation should be completed within one month. Supplementary investigation is limited to two times. After the supplementary investigation is transferred to the people's procuratorate, the people's procuratorate recalculates the time limit for examination and prosecution.

Legal basis:

Article 175th of the Criminal Procedure Law of People's Republic of China (PRC)

Supplementary investigation of a case examined by a people's procuratorate may require the public security organ to provide evidence materials necessary for the trial; If he thinks that there may be cases of collecting evidence by illegal means as stipulated in Article 56 of this Law, he may be required to explain the legality of collecting evidence.

When examining a case, the people's procuratorate may return it to the public security organ for supplementary investigation or conduct its own investigation.

A case under supplementary investigation shall be completed within one month. Supplementary investigation is limited to two times. After the supplementary investigation is transferred to the people's procuratorate, the people's procuratorate recalculates the time limit for examination and prosecution.

If the people's procuratorate still believes that the evidence is insufficient and does not meet the conditions for prosecution in the case of the second supplementary investigation, it shall make a decision not to prosecute.