Of course, the fact that the UK is not already using administrative data in place of censuses indicates it’s not quite as easy as that; there are a variety of problems to be overcome with administrative data including questions of completeness, accuracy, legal feasibility and definitional compatibility.
One of the areas census outputs is in data about journeys to work, which is why ONS’ report is interesting. The census asks a number of questions about employment including place of work and qatar rcs data the way in which people travel to work. Responses enable the construction of a detailed matrix of flows from residences to workplaces, disaggregated by mode of travel and other characteristics. There are no obvious administrative replacements. Taxation data might permit a connection to be made between an individual’s home and their place of work, although it may well be the case that the tax record identifies the location of a business headquarters or payroll department, rather than the location in which the individual actually works. Even if taxation data did identify workplace locations reliably (and could do so for the self-employed as well), there would still be no linkage with mode of travel to work.
A possible way round this problem is to look at big data sources as well as administrative sources, with one example being movement as indicated by changes in mobile phone location data, which is exactly what ONS have studied.