A plot has joint ownerships and undivided legally. It has no legal partition deed. An owner sold his portion to a third party without the consent of rest of all other owners. Now, can the third party (who bought) make the mutation of that plot informing / not-informing the other owners of that plot in Block Land & Land Reform Office legally ?
The municipal body in a city keeps records of property ownership transfers to fix property tax payment liabilities. And this document is a way to ensure that. Mutation of property shows that a property has been transferred from one person to another, and it also assists authorities in fixing taxpayers' responsibility. Although not a legal document, it will be crucial if you want to sell your property in future. Mutation of property in Hindi is called Daakhil-Kharij.