The expanded child tax credit, signed into law by President Biden in March, is an unexpected windfall to many families. For banks, it represents both a short-run test and a longer-term opportunity. The test is that many unbanked households are having trouble accessing their funds in a timely manner, and the Biden administration is asking banks to be part of the solution. On the flip side, parents who do have bank accounts are likely to want advice on what to do with the sudden influx of cash, offering banks a unique customer engagement opportunity. "I think that there's a substantial opportunity for banks and for others to communicate with consumers about this basically free money in their accounts," said Peter Tufano, a finance professor at the University of Oxford's Said Business School who has been surveying U.S. families about the child tax credit.