An Indian census is conducted in two distinct phases. The first is houselisting and the Housing Census, which records every building and dwelling and collects data on housing conditions and household amenities. The second is Population Enumeration, which counts individuals and records their demographic and socio-economic particulars against a fixed reference date. The 16th Census is being spread across 2026 and 2027, with houselisting in 2026 and population enumeration to follow, and different states run the phases on staggered schedules — which is why West Bengal's self-enumeration window opens in August 2026 while the national process began earlier in the year.

Census data underpins far more than a headcount. Delimitation of constituencies, the horizontal devolution formula used by the Finance Commission, the identification of beneficiaries for welfare schemes, and reservation and planning decisions all rest on census figures. India has been working with 2011 data for well over a decade because the 2021 Census was postponed during the pandemic, which means every population-linked allocation has been based on increasingly stale numbers. Moving to a digital census with self-enumeration is also a structural change: it shortens the gap between collection and publication, which has historically run to years.