If the name of the mother-in-law is written on the passbook, the child needs to prove that he is the legal heir or the person who has the right to get the money. This may require some documents and certificates, such as marriage certificate, ID card, household registration book, proof of kinship and so on.

If the child is a minor, it is also necessary to provide the identity certificate of the legal guardian and a statement agreeing to withdraw money. In addition, you need to know the relevant regulations and requirements of the bank where the passbook is located to ensure that the withdrawal process complies with relevant laws, regulations and bank regulations.

In short, it is not easy to take out the money in the mother-in-law's name, and a series of conditions and procedures need to be met. It is recommended to communicate with your family in advance when you need this money to avoid this trouble as much as possible.