<p>The income transfer systems for low-income families in the US and the UK try both to reduce poverty and to encourage work. In-work benefits are a key part of both countries' strategies through the earned income tax credit and the working families' tax credit (and predecessors)respectively. But tax credits are only one part of the whole tax and welfare system. In-work benefits, taxes and welfare benefits combine in both countries to provide good financial incentives for lone parents to do minimum-wage work, but poorer incentives to increase earnings further. But direct comparisons of budget constraints hide important points of detail. First, not enough is known about what determines take-up of in-work benefits. Second, the considerable differences in assessment and payment mechanisms and frequency between EITC and WFTC mean that low-income families in the US and the UK may respond very differently to apparently similar financial incentives.</p>