The ILO seeks to build a harmonized, multi‑country microdata resource to analyse worker transitions between informal and formal employment, including intermediate steps (e.g., for employees being in or outside of the informal sector, written contracts, social‑security registration, access to labour protection such as paid sick or annual leave, tax IDs, and, for the self‑employed, income, simplified bookkeeping, local operating permit/license, etc). The policy objective is to identify the determinants of transitions from informal to formal employment—and reversals back to informality—with a clear view on heterogeneity by socio-demographic characteristic (gender, age, education, region) and importantly employment-related features (status in employment, sector, place of work and size of economic units), and region. The resource will support cross‑country‑comparable transition matrices, event‑history datasets, and both econometric and machine‑learning models to inform targeting and policy design. A multi‑country design is essential to quantify what is common across settings, what is country‑specific, how development stage and institutional capacity shape hazards of formalization, and how policy shifts relate to changes in mobility patterns