This paper studies the relationship between single mothers’ tax credit eligibility and early child development in Britain. Using data from the UK Millennium Cohort Study (MCS), this study finds no relationship between mothers’ entitlements to tax credits and children’s cognitive and non-cognitive outcomes compared to the children of mothers living on welfare. The MCS began as a longitudinal study of children born around 2000 in the UK. The first four waves were used in this study, and thus we have information on each child at approximately 9 months and 3, 5, and 7 years of age. The MCS provides repeated measurement and assessment of children and includes rich information on family's and children's characteristics.