New Delhi, June 30 -- The Centre has asked states and Union territories to make any proposed changes in the boundaries of administrative units before December 31 this year, when they will be considered final for the census exercise, first phase of which will begin on April 1, 2026. In a letter dated June 27 to all states and UTs, registrar general and census commissioner of India Mritunjay Kumar Narayan said that for the census, all villages and towns are divided into uniform enumeration blocks and for each block, an enumerator is assigned to avoid any miss or repetition during the population count. "From April 1, 2026, the Houselisting Operation, the appointment of supervisors and enumerators and the work division among them will be done, and on February 1, 2027, the Census of the population will begin," Narayan said in his letter to chief secretaries of all states and UTs. "It is important that once enumeration blocks are finalised, boundaries of administrative units are not changed." The registrar general further asked the chief secretaries to direct all departments "to make any proposed changes in the boundaries of municipal corporations, revenue villages, tehsils, sub-divisions or districts before December 31". "The states/UTs should ensure that no changes should be made in the boundaries of administrative units between January 1, 2026, and March 31, 2027, during which Census exercise will take place. Any changes in the existing boundaries must be intimated to Census directorates in the states and UTs and Registrar General of India by December 31, 2025. For Census 2027, boundaries of administrative units will be frozen on December 31, 2025," the letter added. To ensure a fair workload for enumerators, an administrative unit is divided into manageable sections for the census called "blocks". A block is a clearly defined area within a village or town on a notional map for census purposes. These are termed houselisting blocks (HLBs) during houselisting operations and enumeration blocks (EBs) during population enumeration and serve as the smallest administrative units for the census. According to the letter, the houselisting operations for the census will begin from April 1, 2026, marking the start of the first phase of the decadal exercise. "Before that, the appointment of supervisors, enumerators and work distribution among them shall be done with cooperation from states and district administration," it said. Earlier this month, the office of registrar general of India (ORGI) in a notification announced that the 16th census, which will also include caste enumeration, will be carried out after a gap of 16 years in 2027, with the reference date of October 1, 2026, in snow-bound areas like Ladakh and March 1, 2027, in the rest of the country. The much-delayed census will be completed by March 1, 2027. Officials have said that while data collection would be over by March 1, 2027, the entire exercise to collate the data and publish it will take two to three more years. On preparatory activities already done, officials said all states have already constituted census coordination committees (CCCs) under the respective chief secretaries. "As the Census exercise was originally to take place in 2020, ORGI had already written to states/UTs for forming CCCs in April 2019," an official said, adding the committees have various departments such as revenue, local administration, municipal corporations, rural development and panchayats, planning education, etc for conducting and monitoring different phases of census. The pre-test for census - which is conducted prior to each census encompassing all facets to check feasibility of all questions, methodologies, logistics arrangements, processing of data, etc - was also done in 2019. The ministry of home affairs (MHA) has said that the 16th census will see involvement of about 3.4 million enumerators and supervisors. Besides, around 130,000 census functionaries would be deployed for the exercise. The ministry further said that the upcoming census "will be conducted through digital means using mobile applications" and "provision of self-enumeration would also be made available to the people"....