This paper introduces the UK Longitudinal Business Database (LBD), a new and experimental business reference database developed by the Office for National Statistics (ONS). It describes the input data, the data linkage and filtering methodology behind the LBD. The LBD is a re-usable longitudinal data spine that is built by using consecutive snapshots of the Inter- Departmental Business Register (IDBR), the UK business register, to capture longitudinality. IDBR unit-specific economic activity criteria are applied to all units of the business structure hierarchy. This process creates the closest measure to date of the active UK business population. The data spine only reflects dynamics embedded in various IDBR snapshots without imposing assumptions to variables that measure business activities. Hence, it provides a flexible, reusable and consistent framework to link firm-level data from administrative and survey sources, via unique identifiers, to create longitudinal linked datasets that suit different user needs. This paper aims to facilitate proper use and understanding of LBD-generated data by ONS-accredited microdata researchers. To aid understanding, it also presents comparisons with existing UK and US business demography datasets, new evidence on firm entry and exit and on the changing distribution of the UK business population at a quarterly frequency, 1999-2022. LBD-created datasets will be accessible to accredited researchers in the ONS Secure Research Service (SRS).
