This paper employs regression discontinuity methods to identify the effect of formality on Brazilian micro-firm performance. The SIMPLES program introduced in November 1996 consolidated multiple taxes and social security contributions into a single payment and reduced taxes for eligible small firms. This provides a quasi-natural experiment that allows us to eliminate many of the endogeneity issues surrounding the impact of formality, measured across several dimensions, on firm performance. We find that SIMPLES had a significant effect on the proportion of firms that have a license to operate, are registered as a legal entity, pay taxes and make social security contributions. Moreover, newly created firms that opt for operating formally achieve higher levels of revenue and profits, employ more workers and are more capital intensive (only for those firms that have employees). The channel through which this occurs is not access to credit or contracts with larger firms. Rather, it appears that the lower cost of contracting labor leads to adopting production techniques that involve greater permanence and a larger paid labor force.