This document provides information about data sources on migration available from the GLA Intelligence Unit. It discusses various administrative data sources like the NHS Central Register and International Passenger Survey that provide information on internal and international migration trends in London. It also summarizes key findings from these sources, like over 30% of London's population being foreign-born. The document outlines the strengths and limitations of different data sources and highlights opportunities from the 2011 Census to improve understanding of migration patterns.