Also called: UDS, Undivided share, Proportionate land share
UDS: the fraction of the land under an apartment building that belongs to each flat owner. You own it jointly with the other owners and cannot mark out your piece.
How it works and what to check
When you buy a flat, you buy the apartment and a share of the land beneath the building. The share is usually worked out in proportion to each flat's area. In Tamil Nadu, Andhra Pradesh, Telangana and Karnataka, the UDS is often stated in square feet in the sale deed, and in Chennai a new flat is commonly bought through a sale deed for the UDS plus a construction agreement for the flat.
UDS matters when a building is redeveloped or acquired, because the land, not the ageing structure, holds most of the value. A builder that adds floors or blocks later can shrink each owner's share.
Check the UDS figure in the deed against the total land area and the number of flats, and ask whether further construction is planned on the same land.
Common questions
Why does UDS matter?
It is your share of the land, which keeps its value as the building ages and decides what you receive in a redevelopment.
Is stamp duty charged on UDS?
Where the UDS is sold under a separate deed, as is common in Chennai, duty is paid on that deed. How construction is charged differs by state.