This paper examines the impact of tax and benefit systems on the incentives for second earners to enter formal employment. The paper highlights how various tax design features create greater participation disincentives for second earners than for primary earners or single individuals. As second earners in OECD countries are more often women, these greater disincentives create significant gender-equity concerns. As second earners are also typically highly responsive to work disincentives, these features are likely to negatively impact economic growth. These disincentives stem from a range of policies including the choice of family-based rather than individual-based taxation, the use of dependent spouse tax credits and allowances, and the use of tax credits and benefits based on family rather than individual income. Reform options to address these issues will depend on countries’ existing tax policy design choices. For countries where individual-based taxation is combined with some family-based provisions, reform of these family-based provisions to lessen their impact on second earner work disincentives may be warranted. For countries with family-based tax systems, the introduction of some individual-based provisions could be considered to mitigate the negative effects of family-based taxation on second earner work incentives.