This study looks at the differences in after-tax low income measure (LIM) statistics from two data sources which both use administrative tax data as their principal inputs: the 2016 Census of Population and the T1 Family file (T1FF). It presents a summary of the two data sources and compares after-tax LIM statistics by focussing on unit of analysis, LIM thresholds and the percentage of population below the LIM. The study also explores what factors users may want to consider when choosing one data source over the other.