This paper studies the incentive effects of social security benefits on labor market informality following a policy reform in Uruguay. The reform extended health benefits to dependent children of private sector salaried workers, and thus altered the incentive structure of holding formal jobs within the household. The identification strategy of the reform’s effects relies on a comparison between workers with children (affected by the reform) and those without children (unaffected by the reform). Difference in differences estimates indicate a substantial effect of this expansion of coverage on informality rates, which fell significantly by about 1.3 percentage points (a 5 percent change) among workers in the treatment group with respect to those in the control group. The evidence also indicates that individuals within households jointly optimized their allocation of labor to the formal and informal sector. Workers responded to the increased incentives for only one member of the household to work in the formal sector. These findings provide evidence of the relevant and substantial incentive effects of social security benefits on the allocation of employment.